From: Yu Kuai <yukuai3@xxxxxxxxxx>
1) initial state, three tasks:
Process 1 Process 2 Process 3
(BIC1) (BIC2) (BIC3)
| Λ | Λ | Λ
| | | | | |
V | V | V |
bfqq1 bfqq2 bfqq3
process ref: 1 1 1
2) bfqq1 merged to bfqq2:
Process 1 Process 2 Process 3
(BIC1) (BIC2) (BIC3)
| | | Λ
\--------------\| | |
V V |
bfqq1--------->bfqq2 bfqq3
process ref: 0 2 1
3) bfqq2 merged to bfqq3:
Process 1 Process 2 Process 3
(BIC1) (BIC2) (BIC3)
here -> Λ | |
\--------------\ \-------------\|
V V
bfqq1--------->bfqq2---------->bfqq3
process ref: 0 1 3
In this case, IO from Process 1 will get bfqq2 from BIC1 first, and then
get bfqq3 through merge chain, and finially handle IO by bfqq3.
Howerver, current code will think bfqq2 is owned by BIC1, like initial
state, and set bfqq2->bic to BIC1.
bfq_insert_request
-> by Process 1
bfqq = bfq_init_rq(rq)
bfqq = bfq_get_bfqq_handle_split
bfqq = bic_to_bfqq
-> get bfqq2 from BIC1
bfqq->ref++
rq->elv.priv[0] = bic
rq->elv.priv[1] = bfqq
if (bfqq_process_refs(bfqq) == 1)
bfqq->bic = bic
-> record BIC1 to bfqq2
__bfq_insert_request
new_bfqq = bfq_setup_cooperator
-> get bfqq3 from bfqq2->new_bfqq
bfqq_request_freed(bfqq)
new_bfqq->ref++
rq->elv.priv[1] = new_bfqq
-> handle IO by bfqq3
Fix the problem by checking bfqq is from merge chain fist. And this
might fix a following problem reported by our syzkaller(unreproducible):
==================================================================
BUG: KASAN: slab-use-after-free in bfq_do_early_stable_merge block/bfq-iosched.c:5692 [inline]
BUG: KASAN: slab-use-after-free in bfq_do_or_sched_stable_merge block/bfq-iosched.c:5805 [inline]
BUG: KASAN: slab-use-after-free in bfq_get_queue+0x25b0/0x2610 block/bfq-iosched.c:5889
Write of size 1 at addr ffff888123839eb8 by task kworker/0:1H/18595
CPU: 0 PID: 18595 Comm: kworker/0:1H Tainted: G L 6.6.0-07439-gba2303cacfda #6
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
Workqueue: kblockd blk_mq_requeue_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x91/0xf0 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0x10d/0x610 mm/kasan/report.c:475
kasan_report+0x8e/0xc0 mm/kasan/report.c:588
bfq_do_early_stable_merge block/bfq-iosched.c:5692 [inline]
bfq_do_or_sched_stable_merge block/bfq-iosched.c:5805 [inline]
bfq_get_queue+0x25b0/0x2610 block/bfq-iosched.c:5889
bfq_get_bfqq_handle_split+0x169/0x5d0 block/bfq-iosched.c:6757
bfq_init_rq block/bfq-iosched.c:6876 [inline]
bfq_insert_request block/bfq-iosched.c:6254 [inline]
bfq_insert_requests+0x1112/0x5cf0 block/bfq-iosched.c:6304
blk_mq_insert_request+0x290/0x8d0 block/blk-mq.c:2593
blk_mq_requeue_work+0x6bc/0xa70 block/blk-mq.c:1502
process_one_work kernel/workqueue.c:2627 [inline]
process_scheduled_works+0x432/0x13f0 kernel/workqueue.c:2700
worker_thread+0x6f2/0x1160 kernel/workqueue.c:2781
kthread+0x33c/0x440 kernel/kthread.c:388
ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:305
</TASK>
Allocated by task 20776:
kasan_save_stack+0x20/0x40 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
__kasan_slab_alloc+0x87/0x90 mm/kasan/common.c:328
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook mm/slab.h:763 [inline]
slab_alloc_node mm/slub.c:3458 [inline]
kmem_cache_alloc_node+0x1a4/0x6f0 mm/slub.c:3503
ioc_create_icq block/blk-ioc.c:370 [inline]
ioc_find_get_icq+0x180/0xaa0 block/blk-ioc.c:436
bfq_prepare_request+0x39/0xf0 block/bfq-iosched.c:6812
blk_mq_rq_ctx_init.isra.7+0x6ac/0xa00 block/blk-mq.c:403
__blk_mq_alloc_requests+0xcc0/0x1070 block/blk-mq.c:517
blk_mq_get_new_requests block/blk-mq.c:2940 [inline]
blk_mq_submit_bio+0x624/0x27c0 block/blk-mq.c:3042
__submit_bio+0x331/0x6f0 block/blk-core.c:624
__submit_bio_noacct_mq block/blk-core.c:703 [inline]
submit_bio_noacct_nocheck+0x816/0xb40 block/blk-core.c:732
submit_bio_noacct+0x7a6/0x1b50 block/blk-core.c:826
xlog_write_iclog+0x7d5/0xa00 fs/xfs/xfs_log.c:1958
xlog_state_release_iclog+0x3b8/0x720 fs/xfs/xfs_log.c:619
xlog_cil_push_work+0x19c5/0x2270 fs/xfs/xfs_log_cil.c:1330
process_one_work kernel/workqueue.c:2627 [inline]
process_scheduled_works+0x432/0x13f0 kernel/workqueue.c:2700
worker_thread+0x6f2/0x1160 kernel/workqueue.c:2781
kthread+0x33c/0x440 kernel/kthread.c:388
ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:305
Freed by task 946:
kasan_save_stack+0x20/0x40 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
kasan_save_free_info+0x2b/0x50 mm/kasan/generic.c:522
____kasan_slab_free mm/kasan/common.c:236 [inline]
__kasan_slab_free+0x12c/0x1c0 mm/kasan/common.c:244
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1815 [inline]
slab_free_freelist_hook mm/slub.c:1841 [inline]
slab_free mm/slub.c:3786 [inline]
kmem_cache_free+0x118/0x6f0 mm/slub.c:3808
rcu_do_batch+0x35c/0xe30 kernel/rcu/tree.c:2189
rcu_core+0x819/0xd90 kernel/rcu/tree.c:2462
__do_softirq+0x1b0/0x7a2 kernel/softirq.c:553
Last potentially related work creation:
kasan_save_stack+0x20/0x40 mm/kasan/common.c:45
__kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
__call_rcu_common kernel/rcu/tree.c:2712 [inline]
call_rcu+0xce/0x1020 kernel/rcu/tree.c:2826
ioc_destroy_icq+0x54c/0x830 block/blk-ioc.c:105
ioc_release_fn+0xf0/0x360 block/blk-ioc.c:124
process_one_work kernel/workqueue.c:2627 [inline]
process_scheduled_works+0x432/0x13f0 kernel/workqueue.c:2700
worker_thread+0x6f2/0x1160 kernel/workqueue.c:2781
kthread+0x33c/0x440 kernel/kthread.c:388
ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:305
Second to last potentially related work creation:
kasan_save_stack+0x20/0x40 mm/kasan/common.c:45
__kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
__call_rcu_common kernel/rcu/tree.c:2712 [inline]
call_rcu+0xce/0x1020 kernel/rcu/tree.c:2826
ioc_destroy_icq+0x54c/0x830 block/blk-ioc.c:105
ioc_release_fn+0xf0/0x360 block/blk-ioc.c:124
process_one_work kernel/workqueue.c:2627 [inline]
process_scheduled_works+0x432/0x13f0 kernel/workqueue.c:2700
worker_thread+0x6f2/0x1160 kernel/workqueue.c:2781
kthread+0x33c/0x440 kernel/kthread.c:388
ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:305
The buggy address belongs to the object at ffff888123839d68
which belongs to the cache bfq_io_cq of size 1360
The buggy address is located 336 bytes inside of
freed 1360-byte region [ffff888123839d68, ffff88812383a2b8)
The buggy address belongs to the physical page:
page:ffffea00048e0e00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88812383f588 pfn:0x123838
head:ffffea00048e0e00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x17ffffc0000a40(workingset|slab|head|node=0|zone=2|lastcpupid=0x1fffff)
page_type: 0xffffffff()
raw: 0017ffffc0000a40 ffff88810588c200 ffffea00048ffa10 ffff888105889488
raw: ffff88812383f588 0000000000150006 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888123839d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888123839e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888123839e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888123839f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888123839f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Fixes: 36eca8948323 ("block, bfq: add Early Queue Merge (EQM)")
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
block/bfq-iosched.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 36a4998c4b37..83adac3e71db 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -6934,7 +6934,8 @@ static struct bfq_queue *bfq_init_rq(struct request *rq)
* addition, if the queue has also just been split, we have to
* resume its state.
*/
- if (likely(bfqq != &bfqd->oom_bfqq) && bfqq_process_refs(bfqq) == 1) {
+ if (likely(bfqq != &bfqd->oom_bfqq) && !bfqq->new_bfqq &&
+ bfqq_process_refs(bfqq) == 1) {
bfqq->bic = bic;
if (split) {
/*
--
2.39.2
