From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 28 Feb 2016 00:17:33 +0000 (-0500)
Subject: do_last(): don't let a bogus return value from ->open() et.al. to confuse us
X-Git-Tag: v4.5-rc6~7^2~3
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=c80567c82ae4814a41287618e315a60ecf513be6;p=linux.git

do_last(): don't let a bogus return value from ->open() et.al. to confuse us

... into returning a positive to path_openat(), which would interpret that
as "symlink had been encountered" and proceed to corrupt memory, etc.
It can only happen due to a bug in some ->open() instance or in some LSM
hook, etc., so we report any such event *and* make sure it doesn't trick
us into further unpleasantness.

Cc: stable@vger.kernel.org # v3.6+, at least
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/namei.c b/fs/namei.c
index f624d132e01e..e30deefad8f8 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3273,6 +3273,10 @@ static int do_last(struct nameidata *nd,
 			goto exit_fput;
 	}
 out:
+	if (unlikely(error > 0)) {
+		WARN_ON(1);
+		error = -EINVAL;
+	}
 	if (got_write)
 		mnt_drop_write(nd->path.mnt);
 	path_put(&save_parent);