linux-kernel - [PATCH 4.9 068/104] Btrfs: fix potential use-after-free for cloned bio

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Date:   Fri,  6 Oct 2017 10:51:46 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Diego <diegocg@...il.com>,
        Liu Bo <bo.li.liu@...cle.com>, David Sterba <dsterba@...e.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 068/104] Btrfs: fix potential use-after-free for cloned bio

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Liu Bo <bo.li.liu@...cle.com>


[ Upstream commit a967efb30b3afa3d858edd6a17f544f9e9e46eea ]

KASAN reports that there is a use-after-free case of bio in btrfs_map_bio.

If we need to submit IOs to several disks at a time, the original bio
would get cloned and mapped to the destination disk, but we really should
use the original bio instead of a cloned bio to do the sanity check
because cloned bios are likely to be freed by its endio.

Reported-by: Diego <diegocg@...il.com>
Signed-off-by: Liu Bo <bo.li.liu@...cle.com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/btrfs/volumes.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6226,7 +6226,7 @@ int btrfs_map_bio(struct btrfs_root *roo
 	for (dev_nr = 0; dev_nr < total_devs; dev_nr++) {
 		dev = bbio->stripes[dev_nr].dev;
 		if (!dev || !dev->bdev ||
-		    (bio_op(bio) == REQ_OP_WRITE && !dev->writeable)) {
+		    (bio_op(first_bio) == REQ_OP_WRITE && !dev->writeable)) {
 			bbio_error(bbio, first_bio, logical);
 			continue;
 		}