[PATCH v4 10/21] fs: Check for invalid i_uid in may_follow_link()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Filesystem uids which don't map into a user namespace may result
in inode->i_uid being INVALID_UID. A symlink and its parent
could have different owners in the filesystem can both get
mapped to INVALID_UID, which may result in following a symlink
when this would not have otherwise been permitted when protected
symlinks are enabled.

Add a new helper function, uid_valid_eq(), and use this to
validate that the ids in may_follow_link() are both equal and
valid. Also add an equivalent helper for gids, which is
currently unused.

Signed-off-by: Seth Forshee <seth.forshee@xxxxxxxxxxxxx>
Acked-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
---
 fs/namei.c             |  2 +-
 include/linux/uidgid.h | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/namei.c b/fs/namei.c
index a29094c6f4a1..6fe8b0d8ca90 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -915,7 +915,7 @@ static inline int may_follow_link(struct nameidata *nd)
 		return 0;
 
 	/* Allowed if parent directory and link owner match. */
-	if (uid_eq(parent->i_uid, inode->i_uid))
+	if (uid_valid_eq(parent->i_uid, inode->i_uid))
 		return 0;
 
 	if (nd->flags & LOOKUP_RCU)
diff --git a/include/linux/uidgid.h b/include/linux/uidgid.h
index 03835522dfcb..e09529fe2668 100644
--- a/include/linux/uidgid.h
+++ b/include/linux/uidgid.h
@@ -117,6 +117,16 @@ static inline bool gid_valid(kgid_t gid)
 	return __kgid_val(gid) != (gid_t) -1;
 }
 
+static inline bool uid_valid_eq(kuid_t left, kuid_t right)
+{
+	return uid_eq(left, right) && uid_valid(left);
+}
+
+static inline bool gid_valid_eq(kgid_t left, kgid_t right)
+{
+	return gid_eq(left, right) && gid_valid(left);
+}
+
 #ifdef CONFIG_USER_NS
 
 extern kuid_t make_kuid(struct user_namespace *from, uid_t uid);
-- 
2.7.4

--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]
  Powered by Linux