From 8e6c96935fcc1ed3dbebc96fddfef3f2f2395afc Mon Sep 17 00:00:00 2001 From: Lucian Adrian Grijincu Date: Tue, 1 Feb 2011 18:42:22 +0200 Subject: [PATCH] security/selinux: fix /proc/sys/ labeling This fixes an old (2007) selinux regression: filesystem labeling for /proc/sys returned -r--r--r-- unknown /proc/sys/fs/file-nr instead of -r--r--r-- system_u:object_r:sysctl_fs_t:s0 /proc/sys/fs/file-nr Events that lead to breaking of /proc/sys/ selinux labeling: 1) sysctl was reimplemented to route all calls through /proc/sys/ commit 77b14db502cb85a031fe8fde6c85d52f3e0acb63 [PATCH] sysctl: reimplement the sysctl proc support 2) proc_dir_entry was removed from ctl_table: commit 3fbfa98112fc3962c416452a0baf2214381030e6 [PATCH] sysctl: remove the proc_dir_entry member for the sysctl tables 3) selinux still walked the proc_dir_entry tree to apply labeling. Because ctl_tables don't have a proc_dir_entry, we did not label /proc/sys/ inodes any more. To achieve this the /proc/sys/ inodes were marked private and private inodes were ignored by selinux. commit bbaca6c2e7ef0f663bc31be4dad7cf530f6c4962 [PATCH] selinux: enhance selinux to always ignore private inodes commit 86a71dbd3e81e8870d0f0e56b87875f57e58222b [PATCH] sysctl: hide the sysctl proc inodes from selinux Access control checks have been done by means of a special sysctl hook that was called for read/write accesses to any /proc/sys/ entry. We don't have to do this because, instead of walking the proc_dir_entry tree we can walk the dentry tree (as done in this patch). With this patch: * we don't mark /proc/sys/ inodes as private * we don't need the sysclt security hook * we walk the dentry tree to find the path to the inode. We have to strip the PID in /proc/PID/ entries that have a proc_dir_entry because selinux does not know how to label paths like '/1/net/rpc/nfsd.fh' (and defaults to 'proc_t' labeling). Selinux does know of '/net/rpc/nfsd.fh' (and applies the 'sysctl_rpc_t' label). PID stripping from the path was done implicitly in the previous code because the proc_dir_entry tree had the root in '/net' in the example from above. The dentry tree has the root in '/1'. Signed-off-by: Eric W. Biederman Signed-off-by: Lucian Adrian Grijincu Signed-off-by: Eric Paris --- fs/proc/proc_sysctl.c | 1 - security/selinux/hooks.c | 120 ++++++--------------------------------- 2 files changed, 18 insertions(+), 103 deletions(-) diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index 09a1f92a34e..fb707e018a8 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -32,7 +32,6 @@ static struct inode *proc_sys_make_inode(struct super_block *sb, ei->sysctl_entry = table; inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; - inode->i_flags |= S_PRIVATE; /* tell selinux to ignore this inode */ inode->i_mode = table->mode; if (!table->child) { inode->i_mode |= S_IFREG; diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 6ae19fd28be..c8b359fc294 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -44,7 +44,6 @@ #include #include #include -#include #include #include #include @@ -71,7 +70,6 @@ #include #include #include -#include #include #include #include @@ -1121,39 +1119,35 @@ static inline u16 socket_type_to_security_class(int family, int type, int protoc } #ifdef CONFIG_PROC_FS -static int selinux_proc_get_sid(struct proc_dir_entry *de, +static int selinux_proc_get_sid(struct dentry *dentry, u16 tclass, u32 *sid) { - int buflen, rc; - char *buffer, *path, *end; + int rc; + char *buffer, *path; buffer = (char *)__get_free_page(GFP_KERNEL); if (!buffer) return -ENOMEM; - buflen = PAGE_SIZE; - end = buffer+buflen; - *--end = '\0'; - buflen--; - path = end-1; - *path = '/'; - while (de && de != de->parent) { - buflen -= de->namelen + 1; - if (buflen < 0) - break; - end -= de->namelen; - memcpy(end, de->name, de->namelen); - *--end = '/'; - path = end; - de = de->parent; + path = dentry_path_raw(dentry, buffer, PAGE_SIZE); + if (IS_ERR(path)) + rc = PTR_ERR(path); + else { + /* each process gets a /proc/PID/ entry. Strip off the + * PID part to get a valid selinux labeling. + * e.g. /proc/1/net/rpc/nfs -> /net/rpc/nfs */ + while (path[1] >= '0' && path[1] <= '9') { + path[1] = '/'; + path++; + } + rc = security_genfs_sid("proc", path, tclass, sid); } - rc = security_genfs_sid("proc", path, tclass, sid); free_page((unsigned long)buffer); return rc; } #else -static int selinux_proc_get_sid(struct proc_dir_entry *de, +static int selinux_proc_get_sid(struct dentry *dentry, u16 tclass, u32 *sid) { @@ -1315,10 +1309,9 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent isec->sid = sbsec->sid; if ((sbsec->flags & SE_SBPROC) && !S_ISLNK(inode->i_mode)) { - struct proc_inode *proci = PROC_I(inode); - if (proci->pde) { + if (opt_dentry) { isec->sclass = inode_mode_to_security_class(inode->i_mode); - rc = selinux_proc_get_sid(proci->pde, + rc = selinux_proc_get_sid(opt_dentry, isec->sclass, &sid); if (rc) @@ -1861,82 +1854,6 @@ static int selinux_capable(struct task_struct *tsk, const struct cred *cred, return task_has_capability(tsk, cred, cap, audit); } -static int selinux_sysctl_get_sid(ctl_table *table, u16 tclass, u32 *sid) -{ - int buflen, rc; - char *buffer, *path, *end; - - rc = -ENOMEM; - buffer = (char *)__get_free_page(GFP_KERNEL); - if (!buffer) - goto out; - - buflen = PAGE_SIZE; - end = buffer+buflen; - *--end = '\0'; - buflen--; - path = end-1; - *path = '/'; - while (table) { - const char *name = table->procname; - size_t namelen = strlen(name); - buflen -= namelen + 1; - if (buflen < 0) - goto out_free; - end -= namelen; - memcpy(end, name, namelen); - *--end = '/'; - path = end; - table = table->parent; - } - buflen -= 4; - if (buflen < 0) - goto out_free; - end -= 4; - memcpy(end, "/sys", 4); - path = end; - rc = security_genfs_sid("proc", path, tclass, sid); -out_free: - free_page((unsigned long)buffer); -out: - return rc; -} - -static int selinux_sysctl(ctl_table *table, int op) -{ - int error = 0; - u32 av; - u32 tsid, sid; - int rc; - - sid = current_sid(); - - rc = selinux_sysctl_get_sid(table, (op == 0001) ? - SECCLASS_DIR : SECCLASS_FILE, &tsid); - if (rc) { - /* Default to the well-defined sysctl SID. */ - tsid = SECINITSID_SYSCTL; - } - - /* The op values are "defined" in sysctl.c, thereby creating - * a bad coupling between this module and sysctl.c */ - if (op == 001) { - error = avc_has_perm(sid, tsid, - SECCLASS_DIR, DIR__SEARCH, NULL); - } else { - av = 0; - if (op & 004) - av |= FILE__READ; - if (op & 002) - av |= FILE__WRITE; - if (av) - error = avc_has_perm(sid, tsid, - SECCLASS_FILE, av, NULL); - } - - return error; -} - static int selinux_quotactl(int cmds, int type, int id, struct super_block *sb) { const struct cred *cred = current_cred(); @@ -5398,7 +5315,6 @@ static struct security_operations selinux_ops = { .ptrace_traceme = selinux_ptrace_traceme, .capget = selinux_capget, .capset = selinux_capset, - .sysctl = selinux_sysctl, .capable = selinux_capable, .quotactl = selinux_quotactl, .quota_on = selinux_quota_on, -- 2.20.1