linux-kernel - [PATCH 5.2 31/45] dm zoned: fix invalid memory access

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Date:   Sun, 29 Sep 2019 15:55:59 +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, Mikulas Patocka <mpatocka@...hat.com>,
        Damien Le Moal <damien.lemoal@....com>,
        Mike Snitzer <snitzer@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.2 31/45] dm zoned: fix invalid memory access

From: Mikulas Patocka <mpatocka@...hat.com>

[ Upstream commit 0c8e9c2d668278652af028c3cc068c65f66342f4 ]

Commit 75d66ffb48efb30f2dd42f041ba8b39c5b2bd115 ("dm zoned: properly
handle backing device failure") triggers a coverity warning:

*** CID 1452808:  Memory - illegal accesses  (USE_AFTER_FREE)
/drivers/md/dm-zoned-target.c: 137 in dmz_submit_bio()
131             clone->bi_private = bioctx;
132
133             bio_advance(bio, clone->bi_iter.bi_size);
134
135             refcount_inc(&bioctx->ref);
136             generic_make_request(clone);
>>>     CID 1452808:  Memory - illegal accesses  (USE_AFTER_FREE)
>>>     Dereferencing freed pointer "clone".
137             if (clone->bi_status == BLK_STS_IOERR)
138                     return -EIO;
139
140             if (bio_op(bio) == REQ_OP_WRITE && dmz_is_seq(zone))
141                     zone->wp_block += nr_blocks;
142

The "clone" bio may be processed and freed before the check
"clone->bi_status == BLK_STS_IOERR" - so this check can access invalid
memory.

Fixes: 75d66ffb48efb3 ("dm zoned: properly handle backing device failure")
Cc: stable@...r.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Reviewed-by: Damien Le Moal <damien.lemoal@....com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/md/dm-zoned-target.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/md/dm-zoned-target.c b/drivers/md/dm-zoned-target.c
index ff3fd011796ed..3334f5865de77 100644
--- a/drivers/md/dm-zoned-target.c
+++ b/drivers/md/dm-zoned-target.c
@@ -133,8 +133,6 @@ static int dmz_submit_bio(struct dmz_target *dmz, struct dm_zone *zone,
 
 	refcount_inc(&bioctx->ref);
 	generic_make_request(clone);
-	if (clone->bi_status == BLK_STS_IOERR)
-		return -EIO;
 
 	if (bio_op(bio) == REQ_OP_WRITE && dmz_is_seq(zone))
 		zone->wp_block += nr_blocks;
-- 
2.20.1