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: v3.12.56~5
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=66efd9e7538d2f5823e7d2ccae2b16e8e57b7d15;p=thirdparty%2Fkernel%2Fstable.git

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

commit c80567c82ae4814a41287618e315a60ecf513be6 upstream.

... 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.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---

diff --git a/fs/namei.c b/fs/namei.c
index d1c0b91b4534b..b1b1781faca15 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3116,6 +3116,10 @@ opened:
 			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);