[PATCH 6.6 007/122] raid1: fix use-after-free for original bio in raid1_write_request()

Greg Kroah-Hartman
2024-04-15T14:34:24Z

From: Yu Kuai <yukuai3@huawei.com>

commit fcf3f7e2fc8a53a6140beee46ec782a4c88e4744 upstream.

r1_bio->bios[] is used to record new bios that will be issued to
underlying disks, however, in raid1_write_request(), r1_bio->bios[]
will set to the original bio temporarily. Meanwhile, if blocked rdev
is set, free_r1bio() will be called causing that all r1_bio->bios[]
to be freed:

raid1_write_request()
r1_bio = alloc_r1bio(mddev, bio); -> r1_bio->bios[] is NULL
for (i = 0; i < disks; i++) -> for each rdev in conf
// first rdev is normal
r1_bio->bios[0] = bio; -> set to original bio
// second rdev is blocked
if (test_bit(Blocked, &rdev->flags))
break

if (blocked_rdev)
free_r1bio()
put_all_bios()
bio_put(r1_bio->bios[0]) -> original bio is freed

Test scripts:

mdadm -CR /dev/md0 -l1 -n4 /dev/sd[abcd] --assume-clean
fio -filename=/dev/md0 -ioengine=libaio -rw=write -bs=4k -numjobs=1 \
-iodepth=128 -name=test -direct=1
echo blocked > /sys/block/md0/md/rd2/state

Test result:

BUG bio-264 (Not tainted): Object already free
-----------------------------------------------------------------------------

Allocated in mempool_alloc_slab+0x24/0x50 age=1 cpu=1 pid=869
kmem_cache_alloc+0x324/0x480
mempool_alloc_slab+0x24/0x50
mempool_alloc+0x6e/0x220
bio_alloc_bioset+0x1af/0x4d0
blkdev_direct_IO+0x164/0x8a0
blkdev_write_iter+0x309/0x440
aio_write+0x139/0x2f0
io_submit_one+0x5ca/0xb70
__do_sys_io_submit+0x86/0x270
__x64_sys_io_submit+0x22/0x30
do_syscall_64+0xb1/0x210
entry_SYSCALL_64_after_hwframe+0x6c/0x74
Freed in mempool_free_slab+0x1f/0x30 age=1 cpu=1 pid=869
kmem_cache_free+0x28c/0x550
mempool_free_slab+0x1f/0x30
mempool_free+0x40/0x100
bio_free+0x59/0x80
bio_put+0xf0/0x220
free_r1bio+0x74/0xb0
raid1_make_request+0xadf/0x1150
md_handle_request+0xc7/0x3b0
md_submit_bio+0x76/0x130
__submit_bio+0xd8/0x1d0
submit_bio_noacct_nocheck+0x1eb/0x5c0
submit_bio_noacct+0x169/0xd40
submit_bio+0xee/0x1d0
blkdev_direct_IO+0x322/0x8a0
blkdev_write_iter+0x309/0x440
aio_write+0x139/0x2f0

Since that bios for underlying disks are not allocated yet, fix this
problem by using mempool_free() directly to free the r1_bio.

Fixes: 992db13a4aee ("md/raid1: free the r1bio before waiting for blocked rdev")
Cc: stable@vger.kernel.org # v6.6+
Reported-by: Coly Li <colyli@suse.de>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Tested-by: Coly Li <colyli@suse.de>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240308093726.1047420-1-yukuai1@huaweicloud.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/md/raid1.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1473,7 +1473,7 @@ static void raid1_write_request(struct m
for (j = 0; j < i; j++)
if (r1_bio->bios[j])
rdev_dec_pending(conf->mirrors[j].rdev, mddev);
- free_r1bio(r1_bio);
+ mempool_free(r1_bio, &conf->r1bio_pool);
allow_barrier(conf, bio->bi_iter.bi_sector);

if (bio->bi_opf & REQ_NOWAIT) {