4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Seth Forshee <seth.fors...@canonical.com>
[ Upstream commit 2d7f9e2ad35e4e7a3086231f19bfab33c6a8a64a ]
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.
Signed-off-by: Seth Forshee <seth.fors...@canonical.com>
Acked-by: Serge Hallyn <serge.hal...@canonical.com>
Signed-off-by: Eric W. Biederman <ebied...@xmission.com>
Signed-off-by: Sasha Levin <alexander.le...@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
fs/namei.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -887,6 +887,7 @@ static inline int may_follow_link(struct
{
const struct inode *inode;
const struct inode *parent;
+ kuid_t puid;
if (!sysctl_protected_symlinks)
return 0;
@@ -902,7 +903,8 @@ static inline int may_follow_link(struct
return 0;
/* Allowed if parent directory and link owner match. */
- if (uid_eq(parent->i_uid, inode->i_uid))
+ puid = parent->i_uid;
+ if (uid_valid(puid) && uid_eq(puid, inode->i_uid))
return 0;
if (nd->flags & LOOKUP_RCU)
