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author | Waiman Long <Waiman.Long@hp.com> | 2014-06-23 11:28:51 -0400 |
---|---|---|
committer | Paul Moore <pmoore@redhat.com> | 2014-06-23 16:52:55 -0400 |
commit | f31e799459659ae88c341aeac16a8a5efb1271d4 (patch) | |
tree | 912cc7f6dd3350c32501a344cf438f7ec2269c72 /security/selinux/ss/services.c | |
parent | 6e51f9cbfa04a92b40e7f9c1e76c8ecbff534a22 (diff) | |
download | linux-f31e799459659ae88c341aeac16a8a5efb1271d4.tar.gz linux-f31e799459659ae88c341aeac16a8a5efb1271d4.tar.bz2 linux-f31e799459659ae88c341aeac16a8a5efb1271d4.zip |
selinux: no recursive read_lock of policy_rwlock in security_genfs_sid()
With the introduction of fair queued rwlock, recursive read_lock()
may hang the offending process if there is a write_lock() somewhere
in between.
With recursive read_lock checking enabled, the following error was
reported:
=============================================
[ INFO: possible recursive locking detected ]
3.16.0-rc1 #2 Tainted: G E
---------------------------------------------
load_policy/708 is trying to acquire lock:
(policy_rwlock){.+.+..}, at: [<ffffffff8125b32a>]
security_genfs_sid+0x3a/0x170
but task is already holding lock:
(policy_rwlock){.+.+..}, at: [<ffffffff8125b48c>]
security_fs_use+0x2c/0x110
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(policy_rwlock);
lock(policy_rwlock);
This patch fixes the occurrence of recursive read_lock() of
policy_rwlock by adding a helper function __security_genfs_sid()
which requires caller to take the lock before calling it. The
security_fs_use() was then modified to call the new helper function.
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <pmoore@redhat.com>
Diffstat (limited to 'security/selinux/ss/services.c')
-rw-r--r-- | security/selinux/ss/services.c | 41 |
1 files changed, 32 insertions, 9 deletions
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c index 4bca49414a40..2aa9d172dc7e 100644 --- a/security/selinux/ss/services.c +++ b/security/selinux/ss/services.c @@ -2277,7 +2277,7 @@ out: } /** - * security_genfs_sid - Obtain a SID for a file in a filesystem + * __security_genfs_sid - Helper to obtain a SID for a file in a filesystem * @fstype: filesystem type * @path: path from root of mount * @sclass: file security class @@ -2286,11 +2286,13 @@ out: * Obtain a SID to use for a file in a filesystem that * cannot support xattr or use a fixed labeling behavior like * transition SIDs or task SIDs. + * + * The caller must acquire the policy_rwlock before calling this function. */ -int security_genfs_sid(const char *fstype, - char *path, - u16 orig_sclass, - u32 *sid) +static inline int __security_genfs_sid(const char *fstype, + char *path, + u16 orig_sclass, + u32 *sid) { int len; u16 sclass; @@ -2301,8 +2303,6 @@ int security_genfs_sid(const char *fstype, while (path[0] == '/' && path[1] == '/') path++; - read_lock(&policy_rwlock); - sclass = unmap_class(orig_sclass); *sid = SECINITSID_UNLABELED; @@ -2336,11 +2336,33 @@ int security_genfs_sid(const char *fstype, *sid = c->sid[0]; rc = 0; out: - read_unlock(&policy_rwlock); return rc; } /** + * security_genfs_sid - Obtain a SID for a file in a filesystem + * @fstype: filesystem type + * @path: path from root of mount + * @sclass: file security class + * @sid: SID for path + * + * Acquire policy_rwlock before calling __security_genfs_sid() and release + * it afterward. + */ +int security_genfs_sid(const char *fstype, + char *path, + u16 orig_sclass, + u32 *sid) +{ + int retval; + + read_lock(&policy_rwlock); + retval = __security_genfs_sid(fstype, path, orig_sclass, sid); + read_unlock(&policy_rwlock); + return retval; +} + +/** * security_fs_use - Determine how to handle labeling for a filesystem. * @sb: superblock in question */ @@ -2370,7 +2392,8 @@ int security_fs_use(struct super_block *sb) } sbsec->sid = c->sid[0]; } else { - rc = security_genfs_sid(fstype, "/", SECCLASS_DIR, &sbsec->sid); + rc = __security_genfs_sid(fstype, "/", SECCLASS_DIR, + &sbsec->sid); if (rc) { sbsec->behavior = SECURITY_FS_USE_NONE; rc = 0; |