From: Seth Forshee <seth.forshee@xxxxxxxxxxxxx>
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.forshee@xxxxxxxxxxxxx>
Acked-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
---
fs/namei.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/namei.c b/fs/namei.c
index 757a32725d92..8701bd9a5270 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -901,6 +901,7 @@ static inline int may_follow_link(struct nameidata *nd)
{
const struct inode *inode;
const struct inode *parent;
+ kuid_t puid;
if (!sysctl_protected_symlinks)
return 0;
@@ -916,7 +917,8 @@ 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))
+ puid = parent->i_uid;
+ if (uid_valid(puid) && uid_eq(puid, inode->i_uid))
return 0;
if (nd->flags & LOOKUP_RCU)
--
2.8.3
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