linux-kernel - [PATCH] vfs: fix linkat error for unprivileged AT_EMPTY

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Message-ID: <20140924152523.GC7441@tucsk.piliscsaba.szeredi.hu>
Date:	Wed, 24 Sep 2014 17:25:23 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH] vfs: fix linkat error for unprivileged AT_EMPTY_PATH

From: Miklos Szeredi <mszeredi@...e.cz>

Return proper error value for linkat(..., AT_EMPTY_PATH) without enough
privileges.

I guess ENOENT was used here, because without AT_EMPTY_PATH that's what
we'd return for an empty path.  But it is wrong for AT_EMPTY_PATH, since we
might not even be passing an empty path, we are simply complaining about
lack of privs for which EPERM is the proper error.

Fixes: 11a7b371b64e ("fs: allow AT_EMPTY_PATH in linkat()...")
Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
Cc: stable@...r.kernel.org # 2.6.39+
---
 fs/namei.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3957,7 +3957,7 @@ SYSCALL_DEFINE5(linkat, int, olddfd, con
 	 */
 	if (flags & AT_EMPTY_PATH) {
 		if (!capable(CAP_DAC_READ_SEARCH))
-			return -ENOENT;
+			return -EPERM;
 		how = LOOKUP_EMPTY;
 	}
 
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