linux-kernel - [ 06/48] fix autofs/afs/etc. magic mountpoint breakage

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Message-Id: <20141116215328.898179262@1wt.eu>
Date:	Sun, 16 Nov 2014 22:53:34 +0100
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Al Viro <viro@...iv.linux.org.uk>, Willy Tarreau <w@....eu>
Subject: [ 06/48] fix autofs/afs/etc. magic mountpoint breakage

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Al Viro <viro@...iv.linux.org.uk>

We end up trying to kfree() nd.last.name on open("/mnt/tmp", O_CREAT)
if /mnt/tmp is an autofs direct mount.  The reason is that nd.last_type
is bogus here; we want LAST_BIND for everything of that kind and we
get LAST_NORM left over from finding parent directory.

So make sure that it *is* set properly; set to LAST_BIND before
doing ->follow_link() - for normal symlinks it will be changed
by __vfs_follow_link() and everything else needs it set that way.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
(cherry picked from commit 86acdca1b63e6890540fa19495cfc708beff3d8b)
[wt: fixes CVE-2014-0203]
Signed-off-by: Willy Tarreau <w@....eu>
---
 fs/namei.c     | 1 +
 fs/proc/base.c | 1 -
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/namei.c b/fs/namei.c
index b0afbd4..0d766d2 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -635,6 +635,7 @@ static __always_inline int __do_follow_link(struct path *path, struct nameidata
 		dget(dentry);
 	}
 	mntget(path->mnt);
+	nd->last_type = LAST_BIND;
 	cookie = dentry->d_inode->i_op->follow_link(dentry, nd);
 	error = PTR_ERR(cookie);
 	if (!IS_ERR(cookie)) {
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 67f7dc0..c75c5cd 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1381,7 +1381,6 @@ static void *proc_pid_follow_link(struct dentry *dentry, struct nameidata *nd)
 		goto out;

 	error = PROC_I(inode)->op.proc_get_link(inode, &nd->path);
-	nd->last_type = LAST_BIND;
 out:
 	return ERR_PTR(error);
 }
-- 
1.7.12.2.21.g234cd45.dirty

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