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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     David Disseldorp <ddiss@suse.de>, Jens Axboe <axboe@kernel.dk>,
        "Sasha Levin" <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.14 027/100] null_blk: fix dev->badblocks leak
Thread-Topic: [PATCH AUTOSEL for 4.14 027/100] null_blk: fix dev->badblocks
 leak
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Date:   Wed, 24 Jan 2018 04:14:36 +0000
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From: David Disseldorp <ddiss@suse.de>

[ Upstream commit 1addb798e93893d33c8dfab743cd44f09fd7719a ]

null_alloc_dev() allocates memory for dev->badblocks, but cleanup
currently only occurs in the configfs release codepath, missing a number
of other places.

This bug was found running the blktests block/010 test, alongside
kmemleak:
rapido1:/blktests# ./check block/010
...
rapido1:/blktests# echo scan > /sys/kernel/debug/kmemleak
[  306.966708] kmemleak: 32 new suspected memory leaks (see /sys/kernel/deb=
ug/kmemleak)
rapido1:/blktests# cat /sys/kernel/debug/kmemleak
unreferenced object 0xffff88001f86d000 (size 4096):
  comm "modprobe", pid 231, jiffies 4294892415 (age 318.252s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff814b0379>] kmemleak_alloc+0x49/0xa0
    [<ffffffff810f180f>] kmem_cache_alloc+0x9f/0xe0
    [<ffffffff8124e45f>] badblocks_init+0x2f/0x60
    [<ffffffffa0019fae>] 0xffffffffa0019fae
    [<ffffffffa0021273>] nullb_device_badblocks_store+0x63/0x130 [null_blk]
    [<ffffffff810004cd>] do_one_initcall+0x3d/0x170
    [<ffffffff8109fe0d>] do_init_module+0x56/0x1e9
    [<ffffffff8109ebd7>] load_module+0x1c47/0x26a0
    [<ffffffff8109f819>] SyS_finit_module+0xa9/0xd0
    [<ffffffff814b4f60>] entry_SYSCALL_64_fastpath+0x13/0x94

Fixes: 2f54a613c942 ("nullb: badbblocks support")
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 drivers/block/null_blk.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index 4d55af5c6e5b..69dfa1d3f453 100644
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -467,7 +467,6 @@ static void nullb_device_release(struct config_item *it=
em)
 {
 	struct nullb_device *dev =3D to_nullb_device(item);
=20
-	badblocks_exit(&dev->badblocks);
 	null_free_device_storage(dev, false);
 	null_free_dev(dev);
 }
@@ -578,6 +577,10 @@ static struct nullb_device *null_alloc_dev(void)
=20
 static void null_free_dev(struct nullb_device *dev)
 {
+	if (!dev)
+		return;
+
+	badblocks_exit(&dev->badblocks);
 	kfree(dev);
 }
=20
--=20
2.11.0