From 334f485df85ac7736ebe14940bf0a059c5f26d7d Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Fri, 9 Sep 2005 13:10:27 -0700 Subject: [PATCH] [PATCH] FUSE - device functions This adds the FUSE device handling functions. This contains the following files: o dev.c - fuse device operations (read, write, release, poll) - registers misc device - support for sending requests to userspace Signed-off-by: Miklos Szeredi Signed-off-by: Adrian Bunk Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/filesystems/fuse.txt | 341 +++++++++++ fs/fuse/Makefile | 2 +- fs/fuse/dev.c | 884 +++++++++++++++++++++++++++++ fs/fuse/fuse_i.h | 223 ++++++++ fs/fuse/inode.c | 58 +- include/linux/fuse.h | 36 +- 6 files changed, 1537 insertions(+), 7 deletions(-) create mode 100644 Documentation/filesystems/fuse.txt create mode 100644 fs/fuse/dev.c diff --git a/Documentation/filesystems/fuse.txt b/Documentation/filesystems/fuse.txt new file mode 100644 index 000000000000..83f96cf56960 --- /dev/null +++ b/Documentation/filesystems/fuse.txt @@ -0,0 +1,341 @@ +Definitions +~~~~~~~~~~~ + +Userspace filesystem: + + A filesystem in which data and metadata are provided by an ordinary + userspace process. The filesystem can be accessed normally through + the kernel interface. + +Filesystem daemon: + + The process(es) providing the data and metadata of the filesystem. + +Non-privileged mount (or user mount): + + A userspace filesystem mounted by a non-privileged (non-root) user. + The filesystem daemon is running with the privileges of the mounting + user. NOTE: this is not the same as mounts allowed with the "user" + option in /etc/fstab, which is not discussed here. + +Mount owner: + + The user who does the mounting. + +User: + + The user who is performing filesystem operations. + +What is FUSE? +~~~~~~~~~~~~~ + +FUSE is a userspace filesystem framework. It consists of a kernel +module (fuse.ko), a userspace library (libfuse.*) and a mount utility +(fusermount). + +One of the most important features of FUSE is allowing secure, +non-privileged mounts. This opens up new possibilities for the use of +filesystems. A good example is sshfs: a secure network filesystem +using the sftp protocol. + +The userspace library and utilities are available from the FUSE +homepage: + + http://fuse.sourceforge.net/ + +Mount options +~~~~~~~~~~~~~ + +'fd=N' + + The file descriptor to use for communication between the userspace + filesystem and the kernel. The file descriptor must have been + obtained by opening the FUSE device ('/dev/fuse'). + +'rootmode=M' + + The file mode of the filesystem's root in octal representation. + +'user_id=N' + + The numeric user id of the mount owner. + +'group_id=N' + + The numeric group id of the mount owner. + +'default_permissions' + + By default FUSE doesn't check file access permissions, the + filesystem is free to implement it's access policy or leave it to + the underlying file access mechanism (e.g. in case of network + filesystems). This option enables permission checking, restricting + access based on file mode. This is option is usually useful + together with the 'allow_other' mount option. + +'allow_other' + + This option overrides the security measure restricting file access + to the user mounting the filesystem. This option is by default only + allowed to root, but this restriction can be removed with a + (userspace) configuration option. + +'kernel_cache' + + This option disables flushing the cache of the file contents on + every open(). This should only be enabled on filesystems, where the + file data is never changed externally (not through the mounted FUSE + filesystem). Thus it is not suitable for network filesystems and + other "intermediate" filesystems. + + NOTE: if this option is not specified (and neither 'direct_io') data + is still cached after the open(), so a read() system call will not + always initiate a read operation. + +'direct_io' + + This option disables the use of page cache (file content cache) in + the kernel for this filesystem. This has several affects: + + - Each read() or write() system call will initiate one or more + read or write operations, data will not be cached in the + kernel. + + - The return value of the read() and write() system calls will + correspond to the return values of the read and write + operations. This is useful for example if the file size is not + known in advance (before reading it). + +'max_read=N' + + With this option the maximum size of read operations can be set. + The default is infinite. Note that the size of read requests is + limited anyway to 32 pages (which is 128kbyte on i386). + +How do non-privileged mounts work? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Since the mount() system call is a privileged operation, a helper +program (fusermount) is needed, which is installed setuid root. + +The implication of providing non-privileged mounts is that the mount +owner must not be able to use this capability to compromise the +system. Obvious requirements arising from this are: + + A) mount owner should not be able to get elevated privileges with the + help of the mounted filesystem + + B) mount owner should not get illegitimate access to information from + other users' and the super user's processes + + C) mount owner should not be able to induce undesired behavior in + other users' or the super user's processes + +How are requirements fulfilled? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + + A) The mount owner could gain elevated privileges by either: + + 1) creating a filesystem containing a device file, then opening + this device + + 2) creating a filesystem containing a suid or sgid application, + then executing this application + + The solution is not to allow opening device files and ignore + setuid and setgid bits when executing programs. To ensure this + fusermount always adds "nosuid" and "nodev" to the mount options + for non-privileged mounts. + + B) If another user is accessing files or directories in the + filesystem, the filesystem daemon serving requests can record the + exact sequence and timing of operations performed. This + information is otherwise inaccessible to the mount owner, so this + counts as an information leak. + + The solution to this problem will be presented in point 2) of C). + + C) There are several ways in which the mount owner can induce + undesired behavior in other users' processes, such as: + + 1) mounting a filesystem over a file or directory which the mount + owner could otherwise not be able to modify (or could only + make limited modifications). + + This is solved in fusermount, by checking the access + permissions on the mountpoint and only allowing the mount if + the mount owner can do unlimited modification (has write + access to the mountpoint, and mountpoint is not a "sticky" + directory) + + 2) Even if 1) is solved the mount owner can change the behavior + of other users' processes. + + i) It can slow down or indefinitely delay the execution of a + filesystem operation creating a DoS against the user or the + whole system. For example a suid application locking a + system file, and then accessing a file on the mount owner's + filesystem could be stopped, and thus causing the system + file to be locked forever. + + ii) It can present files or directories of unlimited length, or + directory structures of unlimited depth, possibly causing a + system process to eat up diskspace, memory or other + resources, again causing DoS. + + The solution to this as well as B) is not to allow processes + to access the filesystem, which could otherwise not be + monitored or manipulated by the mount owner. Since if the + mount owner can ptrace a process, it can do all of the above + without using a FUSE mount, the same criteria as used in + ptrace can be used to check if a process is allowed to access + the filesystem or not. + + Note that the ptrace check is not strictly necessary to + prevent B/2/i, it is enough to check if mount owner has enough + privilege to send signal to the process accessing the + filesystem, since SIGSTOP can be used to get a similar effect. + +I think these limitations are unacceptable? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +If a sysadmin trusts the users enough, or can ensure through other +measures, that system processes will never enter non-privileged +mounts, it can relax the last limitation with a "user_allow_other" +config option. If this config option is set, the mounting user can +add the "allow_other" mount option which disables the check for other +users' processes. + +Kernel - userspace interface +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The following diagram shows how a filesystem operation (in this +example unlink) is performed in FUSE. + +NOTE: everything in this description is greatly simplified + + | "rm /mnt/fuse/file" | FUSE filesystem daemon + | | + | | >sys_read() + | | >fuse_dev_read() + | | >request_wait() + | | [sleep on fc->waitq] + | | + | >sys_unlink() | + | >fuse_unlink() | + | [get request from | + | fc->unused_list] | + | >request_send() | + | [queue req on fc->pending] | + | [wake up fc->waitq] | [woken up] + | >request_wait_answer() | + | [sleep on req->waitq] | + | | pending] + | | [copy req to read buffer] + | | [add req to fc->processing] + | | sys_write() + | | >fuse_dev_write() + | | [look up req in fc->processing] + | | [remove from fc->processing] + | | [copy write buffer to req] + | [woken up] | [wake up req->waitq] + | | unused_list] | + | sys_unlink("/mnt/fuse/file") | + | [acquire inode semaphore | + | for "file"] | + | >fuse_unlink() | + | [sleep on req->waitq] | + | | sys_unlink("/mnt/fuse/file") + | | [acquire inode semaphore + | | for "file"] + | | *DEADLOCK* + +The solution for this is to allow requests to be interrupted while +they are in userspace: + + | [interrupted by signal] | + | fuse_unlink() + | | [queue req on fc->pending] + | | [wake up fc->waitq] + | | [sleep on req->waitq] + +If the filesystem daemon was single threaded, this will stop here, +since there's no other thread to dequeue and execute the request. +In this case the solution is to kill the FUSE daemon as well. If +there are multiple serving threads, you just have to kill them as +long as any remain. + +Moral: a filesystem which deadlocks, can soon find itself dead. + +Scenario 2 - Tricky deadlock +---------------------------- + +This one needs a carefully crafted filesystem. It's a variation on +the above, only the call back to the filesystem is not explicit, +but is caused by a pagefault. + + | Kamikaze filesystem thread 1 | Kamikaze filesystem thread 2 + | | + | [fd = open("/mnt/fuse/file")] | [request served normally] + | [mmap fd to 'addr'] | + | [close fd] | [FLUSH triggers 'magic' flag] + | [read a byte from addr] | + | >do_page_fault() | + | [find or create page] | + | [lock page] | + | >fuse_readpage() | + | [queue READ request] | + | [sleep on req->waitq] | + | | [read request to buffer] + | | [create reply header before addr] + | | >sys_write(addr - headerlength) + | | >fuse_dev_write() + | | [look up req in fc->processing] + | | [remove from fc->processing] + | | [copy write buffer to req] + | | >do_page_fault() + | | [find or create page] + | | [lock page] + | | * DEADLOCK * + +Solution is again to let the the request be interrupted (not +elaborated further). + +An additional problem is that while the write buffer is being +copied to the request, the request must not be interrupted. This +is because the destination address of the copy may not be valid +after the request is interrupted. + +This is solved with doing the copy atomically, and allowing +interruption while the page(s) belonging to the write buffer are +faulted with get_user_pages(). The 'req->locked' flag indicates +when the copy is taking place, and interruption is delayed until +this flag is unset. + diff --git a/fs/fuse/Makefile b/fs/fuse/Makefile index 9c3e4cc7b1a6..21021c356481 100644 --- a/fs/fuse/Makefile +++ b/fs/fuse/Makefile @@ -4,4 +4,4 @@ obj-$(CONFIG_FUSE_FS) += fuse.o -fuse-objs := inode.o +fuse-objs := dev.o inode.o diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c new file mode 100644 index 000000000000..9aaf10a6588f --- /dev/null +++ b/fs/fuse/dev.c @@ -0,0 +1,884 @@ +/* + FUSE: Filesystem in Userspace + Copyright (C) 2001-2005 Miklos Szeredi + + This program can be distributed under the terms of the GNU GPL. + See the file COPYING. +*/ + +#include "fuse_i.h" + +#include +#include +#include +#include +#include +#include +#include +#include + +MODULE_ALIAS_MISCDEV(FUSE_MINOR); + +static kmem_cache_t *fuse_req_cachep; + +static inline struct fuse_conn *fuse_get_conn(struct file *file) +{ + struct fuse_conn *fc; + spin_lock(&fuse_lock); + fc = file->private_data; + if (fc && !fc->sb) + fc = NULL; + spin_unlock(&fuse_lock); + return fc; +} + +static inline void fuse_request_init(struct fuse_req *req) +{ + memset(req, 0, sizeof(*req)); + INIT_LIST_HEAD(&req->list); + init_waitqueue_head(&req->waitq); + atomic_set(&req->count, 1); +} + +struct fuse_req *fuse_request_alloc(void) +{ + struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, SLAB_KERNEL); + if (req) + fuse_request_init(req); + return req; +} + +void fuse_request_free(struct fuse_req *req) +{ + kmem_cache_free(fuse_req_cachep, req); +} + +static inline void block_sigs(sigset_t *oldset) +{ + sigset_t mask; + + siginitsetinv(&mask, sigmask(SIGKILL)); + sigprocmask(SIG_BLOCK, &mask, oldset); +} + +static inline void restore_sigs(sigset_t *oldset) +{ + sigprocmask(SIG_SETMASK, oldset, NULL); +} + +void fuse_reset_request(struct fuse_req *req) +{ + int preallocated = req->preallocated; + BUG_ON(atomic_read(&req->count) != 1); + fuse_request_init(req); + req->preallocated = preallocated; +} + +static void __fuse_get_request(struct fuse_req *req) +{ + atomic_inc(&req->count); +} + +/* Must be called with > 1 refcount */ +static void __fuse_put_request(struct fuse_req *req) +{ + BUG_ON(atomic_read(&req->count) < 2); + atomic_dec(&req->count); +} + +static struct fuse_req *do_get_request(struct fuse_conn *fc) +{ + struct fuse_req *req; + + spin_lock(&fuse_lock); + BUG_ON(list_empty(&fc->unused_list)); + req = list_entry(fc->unused_list.next, struct fuse_req, list); + list_del_init(&req->list); + spin_unlock(&fuse_lock); + fuse_request_init(req); + req->preallocated = 1; + req->in.h.uid = current->fsuid; + req->in.h.gid = current->fsgid; + req->in.h.pid = current->pid; + return req; +} + +struct fuse_req *fuse_get_request(struct fuse_conn *fc) +{ + if (down_interruptible(&fc->outstanding_sem)) + return NULL; + return do_get_request(fc); +} + +/* + * Non-interruptible version of the above function is for operations + * which can't legally return -ERESTART{SYS,NOINTR}. This can still + * return NULL, but only in case the signal is SIGKILL. + */ +struct fuse_req *fuse_get_request_nonint(struct fuse_conn *fc) +{ + int intr; + sigset_t oldset; + + block_sigs(&oldset); + intr = down_interruptible(&fc->outstanding_sem); + restore_sigs(&oldset); + return intr ? NULL : do_get_request(fc); +} + +static void fuse_putback_request(struct fuse_conn *fc, struct fuse_req *req) +{ + spin_lock(&fuse_lock); + if (req->preallocated) + list_add(&req->list, &fc->unused_list); + else + fuse_request_free(req); + + /* If we are in debt decrease that first */ + if (fc->outstanding_debt) + fc->outstanding_debt--; + else + up(&fc->outstanding_sem); + spin_unlock(&fuse_lock); +} + +void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req) +{ + if (atomic_dec_and_test(&req->count)) + fuse_putback_request(fc, req); +} + +/* + * This function is called when a request is finished. Either a reply + * has arrived or it was interrupted (and not yet sent) or some error + * occured during communication with userspace, or the device file was + * closed. It decreases the referece count for the request. In case + * of a background request the referece to the stored objects are + * released. The requester thread is woken up (if still waiting), and + * finally the request is either freed or put on the unused_list + * + * Called with fuse_lock, unlocks it + */ +static void request_end(struct fuse_conn *fc, struct fuse_req *req) +{ + int putback; + req->finished = 1; + putback = atomic_dec_and_test(&req->count); + spin_unlock(&fuse_lock); + if (req->background) { + if (req->inode) + iput(req->inode); + if (req->inode2) + iput(req->inode2); + if (req->file) + fput(req->file); + } + wake_up(&req->waitq); + if (req->in.h.opcode == FUSE_INIT) { + int i; + + if (req->misc.init_in_out.major != FUSE_KERNEL_VERSION) + fc->conn_error = 1; + + /* After INIT reply is received other requests can go + out. So do (FUSE_MAX_OUTSTANDING - 1) number of + up()s on outstanding_sem. The last up() is done in + fuse_putback_request() */ + for (i = 1; i < FUSE_MAX_OUTSTANDING; i++) + up(&fc->outstanding_sem); + } + if (putback) + fuse_putback_request(fc, req); +} + +static void background_request(struct fuse_req *req) +{ + /* Need to get hold of the inode(s) and/or file used in the + request, so FORGET and RELEASE are not sent too early */ + req->background = 1; + if (req->inode) + req->inode = igrab(req->inode); + if (req->inode2) + req->inode2 = igrab(req->inode2); + if (req->file) + get_file(req->file); +} + +static int request_wait_answer_nonint(struct fuse_req *req) +{ + int err; + sigset_t oldset; + block_sigs(&oldset); + err = wait_event_interruptible(req->waitq, req->finished); + restore_sigs(&oldset); + return err; +} + +/* Called with fuse_lock held. Releases, and then reacquires it. */ +static void request_wait_answer(struct fuse_req *req, int interruptible) +{ + int intr; + + spin_unlock(&fuse_lock); + if (interruptible) + intr = wait_event_interruptible(req->waitq, req->finished); + else + intr = request_wait_answer_nonint(req); + spin_lock(&fuse_lock); + if (intr && interruptible && req->sent) { + /* If request is already in userspace, only allow KILL + signal to interrupt */ + spin_unlock(&fuse_lock); + intr = request_wait_answer_nonint(req); + spin_lock(&fuse_lock); + } + if (!intr) + return; + + if (!interruptible || req->sent) + req->out.h.error = -EINTR; + else + req->out.h.error = -ERESTARTNOINTR; + + req->interrupted = 1; + if (req->locked) { + /* This is uninterruptible sleep, because data is + being copied to/from the buffers of req. During + locked state, there mustn't be any filesystem + operation (e.g. page fault), since that could lead + to deadlock */ + spin_unlock(&fuse_lock); + wait_event(req->waitq, !req->locked); + spin_lock(&fuse_lock); + } + if (!req->sent && !list_empty(&req->list)) { + list_del(&req->list); + __fuse_put_request(req); + } else if (!req->finished && req->sent) + background_request(req); +} + +static unsigned len_args(unsigned numargs, struct fuse_arg *args) +{ + unsigned nbytes = 0; + unsigned i; + + for (i = 0; i < numargs; i++) + nbytes += args[i].size; + + return nbytes; +} + +static void queue_request(struct fuse_conn *fc, struct fuse_req *req) +{ + fc->reqctr++; + /* zero is special */ + if (fc->reqctr == 0) + fc->reqctr = 1; + req->in.h.unique = fc->reqctr; + req->in.h.len = sizeof(struct fuse_in_header) + + len_args(req->in.numargs, (struct fuse_arg *) req->in.args); + if (!req->preallocated) { + /* If request is not preallocated (either FORGET or + RELEASE), then still decrease outstanding_sem, so + user can't open infinite number of files while not + processing the RELEASE requests. However for + efficiency do it without blocking, so if down() + would block, just increase the debt instead */ + if (down_trylock(&fc->outstanding_sem)) + fc->outstanding_debt++; + } + list_add_tail(&req->list, &fc->pending); + wake_up(&fc->waitq); +} + +static void request_send_wait(struct fuse_conn *fc, struct fuse_req *req, + int interruptible) +{ + req->isreply = 1; + spin_lock(&fuse_lock); + if (!fc->file) + req->out.h.error = -ENOTCONN; + else if (fc->conn_error) + req->out.h.error = -ECONNREFUSED; + else { + queue_request(fc, req); + /* acquire extra reference, since request is still needed + after request_end() */ + __fuse_get_request(req); + + request_wait_answer(req, interruptible); + } + spin_unlock(&fuse_lock); +} + +void request_send(struct fuse_conn *fc, struct fuse_req *req) +{ + request_send_wait(fc, req, 1); +} + +/* + * Non-interruptible version of the above function is for operations + * which can't legally return -ERESTART{SYS,NOINTR}. This can still + * be interrupted but only with SIGKILL. + */ +void request_send_nonint(struct fuse_conn *fc, struct fuse_req *req) +{ + request_send_wait(fc, req, 0); +} + +static void request_send_nowait(struct fuse_conn *fc, struct fuse_req *req) +{ + spin_lock(&fuse_lock); + if (fc->file) { + queue_request(fc, req); + spin_unlock(&fuse_lock); + } else { + req->out.h.error = -ENOTCONN; + request_end(fc, req); + } +} + +void request_send_noreply(struct fuse_conn *fc, struct fuse_req *req) +{ + req->isreply = 0; + request_send_nowait(fc, req); +} + +void request_send_background(struct fuse_conn *fc, struct fuse_req *req) +{ + req->isreply = 1; + background_request(req); + request_send_nowait(fc, req); +} + +void fuse_send_init(struct fuse_conn *fc) +{ + /* This is called from fuse_read_super() so there's guaranteed + to be a request available */ + struct fuse_req *req = do_get_request(fc); + struct fuse_init_in_out *arg = &req->misc.init_in_out; + arg->major = FUSE_KERNEL_VERSION; + arg->minor = FUSE_KERNEL_MINOR_VERSION; + req->in.h.opcode = FUSE_INIT; + req->in.numargs = 1; + req->in.args[0].size = sizeof(*arg); + req->in.args[0].value = arg; + req->out.numargs = 1; + req->out.args[0].size = sizeof(*arg); + req->out.args[0].value = arg; + request_send_background(fc, req); +} + +/* + * Lock the request. Up to the next unlock_request() there mustn't be + * anything that could cause a page-fault. If the request was already + * interrupted bail out. + */ +static inline int lock_request(struct fuse_req *req) +{ + int err = 0; + if (req) { + spin_lock(&fuse_lock); + if (req->interrupted) + err = -ENOENT; + else + req->locked = 1; + spin_unlock(&fuse_lock); + } + return err; +} + +/* + * Unlock request. If it was interrupted during being locked, the + * requester thread is currently waiting for it to be unlocked, so + * wake it up. + */ +static inline void unlock_request(struct fuse_req *req) +{ + if (req) { + spin_lock(&fuse_lock); + req->locked = 0; + if (req->interrupted) + wake_up(&req->waitq); + spin_unlock(&fuse_lock); + } +} + +struct fuse_copy_state { + int write; + struct fuse_req *req; + const struct iovec *iov; + unsigned long nr_segs; + unsigned long seglen; + unsigned long addr; + struct page *pg; + void *mapaddr; + void *buf; + unsigned len; +}; + +static void fuse_copy_init(struct fuse_copy_state *cs, int write, + struct fuse_req *req, const struct iovec *iov, + unsigned long nr_segs) +{ + memset(cs, 0, sizeof(*cs)); + cs->write = write; + cs->req = req; + cs->iov = iov; + cs->nr_segs = nr_segs; +} + +/* Unmap and put previous page of userspace buffer */ +static inline void fuse_copy_finish(struct fuse_copy_state *cs) +{ + if (cs->mapaddr) { + kunmap_atomic(cs->mapaddr, KM_USER0); + if (cs->write) { + flush_dcache_page(cs->pg); + set_page_dirty_lock(cs->pg); + } + put_page(cs->pg); + cs->mapaddr = NULL; + } +} + +/* + * Get another pagefull of userspace buffer, and map it to kernel + * address space, and lock request + */ +static int fuse_copy_fill(struct fuse_copy_state *cs) +{ + unsigned long offset; + int err; + + unlock_request(cs->req); + fuse_copy_finish(cs); + if (!cs->seglen) { + BUG_ON(!cs->nr_segs); + cs->seglen = cs->iov[0].iov_len; + cs->addr = (unsigned long) cs->iov[0].iov_base; + cs->iov ++; + cs->nr_segs --; + } + down_read(¤t->mm->mmap_sem); + err = get_user_pages(current, current->mm, cs->addr, 1, cs->write, 0, + &cs->pg, NULL); + up_read(¤t->mm->mmap_sem); + if (err < 0) + return err; + BUG_ON(err != 1); + offset = cs->addr % PAGE_SIZE; + cs->mapaddr = kmap_atomic(cs->pg, KM_USER0); + cs->buf = cs->mapaddr + offset; + cs->len = min(PAGE_SIZE - offset, cs->seglen); + cs->seglen -= cs->len; + cs->addr += cs->len; + + return lock_request(cs->req); +} + +/* Do as much copy to/from userspace buffer as we can */ +static inline int fuse_copy_do(struct fuse_copy_state *cs, void **val, + unsigned *size) +{ + unsigned ncpy = min(*size, cs->len); + if (val) { + if (cs->write) + memcpy(cs->buf, *val, ncpy); + else + memcpy(*val, cs->buf, ncpy); + *val += ncpy; + } + *size -= ncpy; + cs->len -= ncpy; + cs->buf += ncpy; + return ncpy; +} + +/* + * Copy a page in the request to/from the userspace buffer. Must be + * done atomically + */ +static inline int fuse_copy_page(struct fuse_copy_state *cs, struct page *page, + unsigned offset, unsigned count, int zeroing) +{ + if (page && zeroing && count < PAGE_SIZE) { + void *mapaddr = kmap_atomic(page, KM_USER1); + memset(mapaddr, 0, PAGE_SIZE); + kunmap_atomic(mapaddr, KM_USER1); + } + while (count) { + int err; + if (!cs->len && (err = fuse_copy_fill(cs))) + return err; + if (page) { + void *mapaddr = kmap_atomic(page, KM_USER1); + void *buf = mapaddr + offset; + offset += fuse_copy_do(cs, &buf, &count); + kunmap_atomic(mapaddr, KM_USER1); + } else + offset += fuse_copy_do(cs, NULL, &count); + } + if (page && !cs->write) + flush_dcache_page(page); + return 0; +} + +/* Copy pages in the request to/from userspace buffer */ +static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes, + int zeroing) +{ + unsigned i; + struct fuse_req *req = cs->req; + unsigned offset = req->page_offset; + unsigned count = min(nbytes, (unsigned) PAGE_SIZE - offset); + + for (i = 0; i < req->num_pages && (nbytes || zeroing); i++) { + struct page *page = req->pages[i]; + int err = fuse_copy_page(cs, page, offset, count, zeroing); + if (err) + return err; + + nbytes -= count; + count = min(nbytes, (unsigned) PAGE_SIZE); + offset = 0; + } + return 0; +} + +/* Copy a single argument in the request to/from userspace buffer */ +static int fuse_copy_one(struct fuse_copy_state *cs, void *val, unsigned size) +{ + while (size) { + int err; + if (!cs->len && (err = fuse_copy_fill(cs))) + return err; + fuse_copy_do(cs, &val, &size); + } + return 0; +} + +/* Copy request arguments to/from userspace buffer */ +static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs, + unsigned argpages, struct fuse_arg *args, + int zeroing) +{ + int err = 0; + unsigned i; + + for (i = 0; !err && i < numargs; i++) { + struct fuse_arg *arg = &args[i]; + if (i == numargs - 1 && argpages) + err = fuse_copy_pages(cs, arg->size, zeroing); + else + err = fuse_copy_one(cs, arg->value, arg->size); + } + return err; +} + +/* Wait until a request is available on the pending list */ +static void request_wait(struct fuse_conn *fc) +{ + DECLARE_WAITQUEUE(wait, current); + + add_wait_queue_exclusive(&fc->waitq, &wait); + while (fc->sb && list_empty(&fc->pending)) { + set_current_state(TASK_INTERRUPTIBLE); + if (signal_pending(current)) + break; + + spin_unlock(&fuse_lock); + schedule(); + spin_lock(&fuse_lock); + } + set_current_state(TASK_RUNNING); + remove_wait_queue(&fc->waitq, &wait); +} + +/* + * Read a single request into the userspace filesystem's buffer. This + * function waits until a request is available, then removes it from + * the pending list and copies request data to userspace buffer. If + * no reply is needed (FORGET) or request has been interrupted or + * there was an error during the copying then it's finished by calling + * request_end(). Otherwise add it to the processing list, and set + * the 'sent' flag. + */ +static ssize_t fuse_dev_readv(struct file *file, const struct iovec *iov, + unsigned long nr_segs, loff_t *off) +{ + int err; + struct fuse_conn *fc; + struct fuse_req *req; + struct fuse_in *in; + struct fuse_copy_state cs; + unsigned reqsize; + + spin_lock(&fuse_lock); + fc = file->private_data; + err = -EPERM; + if (!fc) + goto err_unlock; + request_wait(fc); + err = -ENODEV; + if (!fc->sb) + goto err_unlock; + err = -ERESTARTSYS; + if (list_empty(&fc->pending)) + goto err_unlock; + + req = list_entry(fc->pending.next, struct fuse_req, list); + list_del_init(&req->list); + spin_unlock(&fuse_lock); + + in = &req->in; + reqsize = req->in.h.len; + fuse_copy_init(&cs, 1, req, iov, nr_segs); + err = -EINVAL; + if (iov_length(iov, nr_segs) >= reqsize) { + err = fuse_copy_one(&cs, &in->h, sizeof(in->h)); + if (!err) + err = fuse_copy_args(&cs, in->numargs, in->argpages, + (struct fuse_arg *) in->args, 0); + } + fuse_copy_finish(&cs); + + spin_lock(&fuse_lock); + req->locked = 0; + if (!err && req->interrupted) + err = -ENOENT; + if (err) { + if (!req->interrupted) + req->out.h.error = -EIO; + request_end(fc, req); + return err; + } + if (!req->isreply) + request_end(fc, req); + else { + req->sent = 1; + list_add_tail(&req->list, &fc->processing); + spin_unlock(&fuse_lock); + } + return reqsize; + + err_unlock: + spin_unlock(&fuse_lock); + return err; +} + +static ssize_t fuse_dev_read(struct file *file, char __user *buf, + size_t nbytes, loff_t *off) +{ + struct iovec iov; + iov.iov_len = nbytes; + iov.iov_base = buf; + return fuse_dev_readv(file, &iov, 1, off); +} + +/* Look up request on processing list by unique ID */ +static struct fuse_req *request_find(struct fuse_conn *fc, u64 unique) +{ + struct list_head *entry; + + list_for_each(entry, &fc->processing) { + struct fuse_req *req; + req = list_entry(entry, struct fuse_req, list); + if (req->in.h.unique == unique) + return req; + } + return NULL; +} + +static int copy_out_args(struct fuse_copy_state *cs, struct fuse_out *out, + unsigned nbytes) +{ + unsigned reqsize = sizeof(struct fuse_out_header); + + if (out->h.error) + return nbytes != reqsize ? -EINVAL : 0; + + reqsize += len_args(out->numargs, out->args); + + if (reqsize < nbytes || (reqsize > nbytes && !out->argvar)) + return -EINVAL; + else if (reqsize > nbytes) { + struct fuse_arg *lastarg = &out->args[out->numargs-1]; + unsigned diffsize = reqsize - nbytes; + if (diffsize > lastarg->size) + return -EINVAL; + lastarg->size -= diffsize; + } + return fuse_copy_args(cs, out->numargs, out->argpages, out->args, + out->page_zeroing); +} + +/* + * Write a single reply to a request. First the header is copied from + * the write buffer. The request is then searched on the processing + * list by the unique ID found in the header. If found, then remove + * it from the list and copy the rest of the buffer to the request. + * The request is finished by calling request_end() + */ +static ssize_t fuse_dev_writev(struct file *file, const struct iovec *iov, + unsigned long nr_segs, loff_t *off) +{ + int err; + unsigned nbytes = iov_length(iov, nr_segs); + struct fuse_req *req; + struct fuse_out_header oh; + struct fuse_copy_state cs; + struct fuse_conn *fc = fuse_get_conn(file); + if (!fc) + return -ENODEV; + + fuse_copy_init(&cs, 0, NULL, iov, nr_segs); + if (nbytes < sizeof(struct fuse_out_header)) + return -EINVAL; + + err = fuse_copy_one(&cs, &oh, sizeof(oh)); + if (err) + goto err_finish; + err = -EINVAL; + if (!oh.unique || oh.error <= -1000 || oh.error > 0 || + oh.len != nbytes) + goto err_finish; + + spin_lock(&fuse_lock); + req = request_find(fc, oh.unique); + err = -EINVAL; + if (!req) + goto err_unlock; + + list_del_init(&req->list); + if (req->interrupted) { + request_end(fc, req); + fuse_copy_finish(&cs); + return -ENOENT; + } + req->out.h = oh; + req->locked = 1; + cs.req = req; + spin_unlock(&fuse_lock); + + err = copy_out_args(&cs, &req->out, nbytes); + fuse_copy_finish(&cs); + + spin_lock(&fuse_lock); + req->locked = 0; + if (!err) { + if (req->interrupted) + err = -ENOENT; + } else if (!req->interrupted) + req->out.h.error = -EIO; + request_end(fc, req); + + return err ? err : nbytes; + + err_unlock: + spin_unlock(&fuse_lock); + err_finish: + fuse_copy_finish(&cs); + return err; +} + +static ssize_t fuse_dev_write(struct file *file, const char __user *buf, + size_t nbytes, loff_t *off) +{ + struct iovec iov; + iov.iov_len = nbytes; + iov.iov_base = (char __user *) buf; + return fuse_dev_writev(file, &iov, 1, off); +} + +static unsigned fuse_dev_poll(struct file *file, poll_table *wait) +{ + struct fuse_conn *fc = fuse_get_conn(file); + unsigned mask = POLLOUT | POLLWRNORM; + + if (!fc) + return -ENODEV; + + poll_wait(file, &fc->waitq, wait); + + spin_lock(&fuse_lock); + if (!list_empty(&fc->pending)) + mask |= POLLIN | POLLRDNORM; + spin_unlock(&fuse_lock); + + return mask; +} + +/* Abort all requests on the given list (pending or processing) */ +static void end_requests(struct fuse_conn *fc, struct list_head *head) +{ + while (!list_empty(head)) { + struct fuse_req *req; + req = list_entry(head->next, struct fuse_req, list); + list_del_init(&req->list); + req->out.h.error = -ECONNABORTED; + request_end(fc, req); + spin_lock(&fuse_lock); + } +} + +static int fuse_dev_release(struct inode *inode, struct file *file) +{ + struct fuse_conn *fc; + + spin_lock(&fuse_lock); + fc = file->private_data; + if (fc) { + fc->file = NULL; + end_requests(fc, &fc->pending); + end_requests(fc, &fc->processing); + fuse_release_conn(fc); + } + spin_unlock(&fuse_lock); + return 0; +} + +struct file_operations fuse_dev_operations = { + .owner = THIS_MODULE, + .llseek = no_llseek, + .read = fuse_dev_read, + .readv = fuse_dev_readv, + .write = fuse_dev_write, + .writev = fuse_dev_writev, + .poll = fuse_dev_poll, + .release = fuse_dev_release, +}; + +static struct miscdevice fuse_miscdevice = { + .minor = FUSE_MINOR, + .name = "fuse", + .fops = &fuse_dev_operations, +}; + +int __init fuse_dev_init(void) +{ + int err = -ENOMEM; + fuse_req_cachep = kmem_cache_create("fuse_request", + sizeof(struct fuse_req), + 0, 0, NULL, NULL); + if (!fuse_req_cachep) + goto out; + + err = misc_register(&fuse_miscdevice); + if (err) + goto out_cache_clean; + + return 0; + + out_cache_clean: + kmem_cache_destroy(fuse_req_cachep); + out: + return err; +} + +void fuse_dev_cleanup(void) +{ + misc_deregister(&fuse_miscdevice); + kmem_cache_destroy(fuse_req_cachep); +} diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index eed6e89ce01f..50ad6a0c39bf 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -15,6 +15,12 @@ #include #include +/** Max number of pages that can be used in a single read request */ +#define FUSE_MAX_PAGES_PER_REQ 32 + +/** If more requests are outstanding, then the operation will block */ +#define FUSE_MAX_OUTSTANDING 10 + /** FUSE inode */ struct fuse_inode { /** Inode data */ @@ -28,6 +34,123 @@ struct fuse_inode { unsigned long i_time; }; +/** One input argument of a request */ +struct fuse_in_arg { + unsigned size; + const void *value; +}; + +/** The request input */ +struct fuse_in { + /** The request header */ + struct fuse_in_header h; + + /** True if the data for the last argument is in req->pages */ + unsigned argpages:1; + + /** Number of arguments */ + unsigned numargs; + + /** Array of arguments */ + struct fuse_in_arg args[3]; +}; + +/** One output argument of a request */ +struct fuse_arg { + unsigned size; + void *value; +}; + +/** The request output */ +struct fuse_out { + /** Header returned from userspace */ + struct fuse_out_header h; + + /** Last argument is variable length (can be shorter than + arg->size) */ + unsigned argvar:1; + + /** Last argument is a list of pages to copy data to */ + unsigned argpages:1; + + /** Zero partially or not copied pages */ + unsigned page_zeroing:1; + + /** Number or arguments */ + unsigned numargs; + + /** Array of arguments */ + struct fuse_arg args[3]; +}; + +struct fuse_req; +struct fuse_conn; + +/** + * A request to the client + */ +struct fuse_req { + /** This can be on either unused_list, pending or processing + lists in fuse_conn */ + struct list_head list; + + /** refcount */ + atomic_t count; + + /** True if the request has reply */ + unsigned isreply:1; + + /** The request is preallocated */ + unsigned preallocated:1; + + /** The request was interrupted */ + unsigned interrupted:1; + + /** Request is sent in the background */ + unsigned background:1; + + /** Data is being copied to/from the request */ + unsigned locked:1; + + /** Request has been sent to userspace */ + unsigned sent:1; + + /** The request is finished */ + unsigned finished:1; + + /** The request input */ + struct fuse_in in; + + /** The request output */ + struct fuse_out out; + + /** Used to wake up the task waiting for completion of request*/ + wait_queue_head_t waitq; + + /** Data for asynchronous requests */ + union { + struct fuse_init_in_out init_in_out; + } misc; + + /** page vector */ + struct page *pages[FUSE_MAX_PAGES_PER_REQ]; + + /** number of pages in vector */ + unsigned num_pages; + + /** offset of data on first page */ + unsigned page_offset; + + /** Inode used in the request */ + struct inode *inode; + + /** Second inode used in the request (or NULL) */ + struct inode *inode2; + + /** File used in the request (or NULL) */ + struct file *file; +}; + /** * A Fuse connection. * @@ -39,9 +162,37 @@ struct fuse_conn { /** The superblock of the mounted filesystem */ struct super_block *sb; + /** The opened client device */ + struct file *file; + /** The user id for this mount */ uid_t user_id; + /** Readers of the connection are waiting on this */ + wait_queue_head_t waitq; + + /** The list of pending requests */ + struct list_head pending; + + /** The list of requests being processed */ + struct list_head processing; + + /** Controls the maximum number of outstanding requests */ + struct semaphore outstanding_sem; + + /** This counts the number of outstanding requests if + outstanding_sem would go negative */ + unsigned outstanding_debt; + + /** The list of unused requests */ + struct list_head unused_list; + + /** The next unique request id */ + u64 reqctr; + + /** Connection failed (version mismatch) */ + unsigned conn_error : 1; + /** Backing dev info */ struct backing_dev_info bdi; }; @@ -71,13 +222,20 @@ static inline u64 get_node_id(struct inode *inode) return get_fuse_inode(inode)->nodeid; } +/** Device operations */ +extern struct file_operations fuse_dev_operations; + /** * This is the single global spinlock which protects FUSE's structures * * The following data is protected by this lock: * + * - the private_data field of the device file * - the s_fs_info field of the super block + * - unused_list, pending, processing lists in fuse_conn + * - the unique request ID counter reqctr in fuse_conn * - the sb (super_block) field in fuse_conn + * - the file (device file) field in fuse_conn */ extern spinlock_t fuse_lock; @@ -87,3 +245,68 @@ extern spinlock_t fuse_lock; */ void fuse_release_conn(struct fuse_conn *fc); +/** + * Initialize the client device + */ +int fuse_dev_init(void); + +/** + * Cleanup the client device + */ +void fuse_dev_cleanup(void); + +/** + * Allocate a request + */ +struct fuse_req *fuse_request_alloc(void); + +/** + * Free a request + */ +void fuse_request_free(struct fuse_req *req); + +/** + * Reinitialize a request, the preallocated flag is left unmodified + */ +void fuse_reset_request(struct fuse_req *req); + +/** + * Reserve a preallocated request + */ +struct fuse_req *fuse_get_request(struct fuse_conn *fc); + +/** + * Reserve a preallocated request, only interruptible by SIGKILL + */ +struct fuse_req *fuse_get_request_nonint(struct fuse_conn *fc); + +/** + * Decrement reference count of a request. If count goes to zero put + * on unused list (preallocated) or free reqest (not preallocated). + */ +void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req); + +/** + * Send a request (synchronous, interruptible) + */ +void request_send(struct fuse_conn *fc, struct fuse_req *req); + +/** + * Send a request (synchronous, non-interruptible except by SIGKILL) + */ +void request_send_nonint(struct fuse_conn *fc, struct fuse_req *req); + +/** + * Send a request with no reply + */ +void request_send_noreply(struct fuse_conn *fc, struct fuse_req *req); + +/** + * Send a request in the background + */ +void request_send_background(struct fuse_conn *fc, struct fuse_req *req); + +/** + * Send the INIT message + */ +void fuse_send_init(struct fuse_conn *fc); diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index ea6339c2b6a1..33fad334ba70 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -151,6 +151,8 @@ static void fuse_put_super(struct super_block *sb) mount_count --; fc->sb = NULL; fc->user_id = 0; + /* Flush all readers on this fs */ + wake_up_all(&fc->waitq); fuse_release_conn(fc); *get_fuse_conn_super_p(sb) = NULL; spin_unlock(&fuse_lock); @@ -229,22 +231,51 @@ static int fuse_show_options(struct seq_file *m, struct vfsmount *mnt) return 0; } -void fuse_release_conn(struct fuse_conn *fc) +static void free_conn(struct fuse_conn *fc) { + while (!list_empty(&fc->unused_list)) { + struct fuse_req *req; + req = list_entry(fc->unused_list.next, struct fuse_req, list); + list_del(&req->list); + fuse_request_free(req); + } kfree(fc); } +/* Must be called with the fuse lock held */ +void fuse_release_conn(struct fuse_conn *fc) +{ + if (!fc->sb && !fc->file) + free_conn(fc); +} + static struct fuse_conn *new_conn(void) { struct fuse_conn *fc; fc = kmalloc(sizeof(*fc), GFP_KERNEL); if (fc != NULL) { + int i; memset(fc, 0, sizeof(*fc)); fc->sb = NULL; + fc->file = NULL; fc->user_id = 0; + init_waitqueue_head(&fc->waitq); + INIT_LIST_HEAD(&fc->pending); + INIT_LIST_HEAD(&fc->processing); + INIT_LIST_HEAD(&fc->unused_list); + sema_init(&fc->outstanding_sem, 0); + for (i = 0; i < FUSE_MAX_OUTSTANDING; i++) { + struct fuse_req *req = fuse_request_alloc(); + if (!req) { + free_conn(fc); + return NULL; + } + list_add(&req->list, &fc->unused_list); + } fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE; fc->bdi.unplug_io_fn = default_unplug_io_fn; + fc->reqctr = 0; } return fc; } @@ -253,11 +284,20 @@ static struct fuse_conn *get_conn(struct file *file, struct super_block *sb) { struct fuse_conn *fc; + if (file->f_op != &fuse_dev_operations) + return ERR_PTR(-EINVAL); fc = new_conn(); if (fc == NULL) - return NULL; + return ERR_PTR(-ENOMEM); spin_lock(&fuse_lock); - fc->sb = sb; + if (file->private_data) { + free_conn(fc); + fc = ERR_PTR(-EINVAL); + } else { + file->private_data = fc; + fc->sb = sb; + fc->file = file; + } spin_unlock(&fuse_lock); return fc; } @@ -315,8 +355,8 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent) fc = get_conn(file, sb); fput(file); - if (fc == NULL) - return -EINVAL; + if (IS_ERR(fc)) + return PTR_ERR(fc); fc->user_id = d.user_id; @@ -336,6 +376,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent) iput(root); goto err; } + fuse_send_init(fc); return 0; err: @@ -411,8 +452,14 @@ static int __init fuse_init(void) if (res) goto err; + res = fuse_dev_init(); + if (res) + goto err_fs_cleanup; + return 0; + err_fs_cleanup: + fuse_fs_cleanup(); err: return res; } @@ -422,6 +469,7 @@ static void __exit fuse_exit(void) printk(KERN_DEBUG "fuse exit\n"); fuse_fs_cleanup(); + fuse_dev_cleanup(); } module_init(fuse_init); diff --git a/include/linux/fuse.h b/include/linux/fuse.h index 2b1f4ae01e9d..a1aebd7104c4 100644 --- a/include/linux/fuse.h +++ b/include/linux/fuse.h @@ -11,7 +11,7 @@ #include /** Version number of this interface */ -#define FUSE_KERNEL_VERSION 5 +#define FUSE_KERNEL_VERSION 6 /** Minor version number of this interface */ #define FUSE_KERNEL_MINOR_VERSION 1 @@ -19,6 +19,12 @@ /** The node ID of the root inode */ #define FUSE_ROOT_ID 1 +/** The major number of the fuse character device */ +#define FUSE_MAJOR 10 + +/** The minor number of the fuse character device */ +#define FUSE_MINOR 229 + struct fuse_attr { __u64 ino; __u64 size; @@ -36,3 +42,31 @@ struct fuse_attr { __u32 rdev; }; +enum fuse_opcode { + FUSE_INIT = 26 +}; + +/* Conservative buffer size for the client */ +#define FUSE_MAX_IN 8192 + +struct fuse_init_in_out { + __u32 major; + __u32 minor; +}; + +struct fuse_in_header { + __u32 len; + __u32 opcode; + __u64 unique; + __u64 nodeid; + __u32 uid; + __u32 gid; + __u32 pid; +}; + +struct fuse_out_header { + __u32 len; + __s32 error; + __u64 unique; +}; + -- 2.20.1