v1->v2:
- Add an internal helper to switch on/off lock acquisition instead
of modifying the external API.
With 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 in security_genfs_sid() by adding a helper function
which has a 5th argument to indicate if the rwlock has been taken.
Signed-off-by: Waiman Long <waiman.l...@hp.com>
---
security/selinux/ss/services.c | 36 ++++++++++++++++++++++++++++--------
1 files changed, 28 insertions(+), 8 deletions(-)
diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 4bca494..5f4c1f3 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -2277,20 +2277,22 @@ 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
* @sid: SID for path
+ * @locked: true if policy_rwlock taken
*
* 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.
*/
-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 locked)
{
int len;
u16 sclass;
@@ -2301,7 +2303,8 @@ int security_genfs_sid(const char *fstype,
while (path[0] == '/' && path[1] == '/')
path++;
- read_lock(&policy_rwlock);
+ if (!locked)
+ read_lock(&policy_rwlock);
sclass = unmap_class(orig_sclass);
*sid = SECINITSID_UNLABELED;
@@ -2336,11 +2339,27 @@ int security_genfs_sid(const char *fstype,
*sid = c->sid[0];
rc = 0;
out:
- read_unlock(&policy_rwlock);
+ if (!locked)
+ 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
+ */
+int security_genfs_sid(const char *fstype,
+ char *path,
+ u16 orig_sclass,
+ u32 *sid)
+{
+ return __security_genfs_sid(fstype, path, orig_sclass, sid, false);
+}
+
+/**
* security_fs_use - Determine how to handle labeling for a filesystem.
* @sb: superblock in question
*/
@@ -2370,7 +2389,8 @@ 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, true);
if (rc) {
sbsec->behavior = SECURITY_FS_USE_NONE;
rc = 0;
--
1.7.1
--
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