From 64a07bd82ed526d813b64b0957543eef55bdf9c0 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Sun, 26 Mar 2006 01:36:55 -0800 Subject: [PATCH] [PATCH] protect remove_proc_entry It has been discovered that the remove_proc_entry has a race in the removing of entries in the proc file system that are siblings. There's no protection around the traversing and removing of elements that belong in the same subdirectory. This subdirectory list is protected in other areas by the BKL. So the BKL was at first used to protect this area too, but unfortunately, remove_proc_entry may be called with spinlocks held. The BKL may schedule, so this was not a solution. The final solution was to add a new global spin lock to protect this list, called proc_subdir_lock. This lock now protects the list in remove_proc_entry, and I also went around looking for other areas that this list is modified and added this protection there too. Care must be taken since these locations call several functions that may also schedule. Since I don't see any location that these functions that modify the subdirectory list are called by interrupts, the irqsave/restore versions of the spin lock was _not_ used. Signed-off-by: Steven Rostedt Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/generic.c | 32 +++++++++++++++++++++++++++++--- fs/proc/proc_devtree.c | 2 ++ include/linux/proc_fs.h | 3 +++ 3 files changed, 34 insertions(+), 3 deletions(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index 20e5c4509a43..47b7a20d45eb 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include "internal.h" @@ -29,6 +30,8 @@ static ssize_t proc_file_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos); static loff_t proc_file_lseek(struct file *, loff_t, int); +DEFINE_SPINLOCK(proc_subdir_lock); + int proc_match(int len, const char *name, struct proc_dir_entry *de) { if (de->namelen != len) @@ -277,7 +280,9 @@ static int xlate_proc_name(const char *name, const char *cp = name, *next; struct proc_dir_entry *de; int len; + int rtn = 0; + spin_lock(&proc_subdir_lock); de = &proc_root; while (1) { next = strchr(cp, '/'); @@ -289,13 +294,17 @@ static int xlate_proc_name(const char *name, if (proc_match(len, cp, de)) break; } - if (!de) - return -ENOENT; + if (!de) { + rtn = -ENOENT; + goto out; + } cp += len + 1; } *residual = cp; *ret = de; - return 0; +out: + spin_unlock(&proc_subdir_lock); + return rtn; } static DEFINE_IDR(proc_inum_idr); @@ -380,6 +389,7 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam int error = -ENOENT; lock_kernel(); + spin_lock(&proc_subdir_lock); de = PDE(dir); if (de) { for (de = de->subdir; de ; de = de->next) { @@ -388,12 +398,15 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam if (!memcmp(dentry->d_name.name, de->name, de->namelen)) { unsigned int ino = de->low_ino; + spin_unlock(&proc_subdir_lock); error = -EINVAL; inode = proc_get_inode(dir->i_sb, ino, de); + spin_lock(&proc_subdir_lock); break; } } } + spin_unlock(&proc_subdir_lock); unlock_kernel(); if (inode) { @@ -447,11 +460,13 @@ int proc_readdir(struct file * filp, filp->f_pos++; /* fall through */ default: + spin_lock(&proc_subdir_lock); de = de->subdir; i -= 2; for (;;) { if (!de) { ret = 1; + spin_unlock(&proc_subdir_lock); goto out; } if (!i) @@ -461,12 +476,16 @@ int proc_readdir(struct file * filp, } do { + /* filldir passes info to user space */ + spin_unlock(&proc_subdir_lock); if (filldir(dirent, de->name, de->namelen, filp->f_pos, de->low_ino, de->mode >> 12) < 0) goto out; + spin_lock(&proc_subdir_lock); filp->f_pos++; de = de->next; } while (de); + spin_unlock(&proc_subdir_lock); } ret = 1; out: unlock_kernel(); @@ -500,9 +519,13 @@ static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp if (i == 0) return -EAGAIN; dp->low_ino = i; + + spin_lock(&proc_subdir_lock); dp->next = dir->subdir; dp->parent = dir; dir->subdir = dp; + spin_unlock(&proc_subdir_lock); + if (S_ISDIR(dp->mode)) { if (dp->proc_iops == NULL) { dp->proc_fops = &proc_dir_operations; @@ -694,6 +717,8 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent) if (!parent && xlate_proc_name(name, &parent, &fn) != 0) goto out; len = strlen(fn); + + spin_lock(&proc_subdir_lock); for (p = &parent->subdir; *p; p=&(*p)->next ) { if (!proc_match(len, fn, *p)) continue; @@ -714,6 +739,7 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent) } break; } + spin_unlock(&proc_subdir_lock); out: return; } diff --git a/fs/proc/proc_devtree.c b/fs/proc/proc_devtree.c index 9bdd077d6f55..596b4b4f1cc8 100644 --- a/fs/proc/proc_devtree.c +++ b/fs/proc/proc_devtree.c @@ -136,9 +136,11 @@ void proc_device_tree_add_node(struct device_node *np, * properties are quite unimportant for us though, thus we * simply "skip" them here, but we do have to check. */ + spin_lock(&proc_subdir_lock); for (ent = de->subdir; ent != NULL; ent = ent->next) if (!strcmp(ent->name, pp->name)) break; + spin_unlock(&proc_subdir_lock); if (ent != NULL) { printk(KERN_WARNING "device-tree: property \"%s\" name" " conflicts with node in %s\n", pp->name, diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h index aa6322d45198..6b12b0f661b4 100644 --- a/include/linux/proc_fs.h +++ b/include/linux/proc_fs.h @@ -4,6 +4,7 @@ #include #include #include +#include #include /* @@ -92,6 +93,8 @@ extern struct proc_dir_entry *proc_bus; extern struct proc_dir_entry *proc_root_driver; extern struct proc_dir_entry *proc_root_kcore; +extern spinlock_t proc_subdir_lock; + extern void proc_root_init(void); extern void proc_misc_init(void); -- 2.20.1