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Commit 2d7f9e2a authored by Seth Forshee's avatar Seth Forshee Committed by Eric W. Biederman
Browse files

fs: Check for invalid i_uid in may_follow_link() 



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: default avatarSeth Forshee <seth.forshee@canonical.com>
Acked-by: default avatarSerge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent 0d4d717f

fs/namei.c

+3 −1
Original line number Diff line number Diff line
@@ -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)