Re: [PATCH] blk-mq: don't free tags if the tag_set is used by other device in queue initialztion
From: Ming Lei
Date: Sun Nov 07 2021 - 21:16:48 EST
On Mon, Nov 08, 2021 at 10:08:52AM +0800, yebin wrote:
>
>
> On 2021/11/8 9:31, Ming Lei wrote:
> > On Sat, Nov 06, 2021 at 05:23:31PM +0800, Yu Kuai wrote:
> > > Our test report a UAF on v5.10:
> > >
> > > [ 1446.674930] ==================================================================
> > > [ 1446.675970] BUG: KASAN: use-after-free in blk_mq_get_driver_tag+0x9a4/0xa90
> > > [ 1446.676902] Read of size 8 at addr ffff8880185afd10 by task kworker/1:2/12348
> > > [ 1446.677851]
> > > [ 1446.678073] CPU: 1 PID: 12348 Comm: kworker/1:2 Not tainted 5.10.0-10177-gc9c81b1e346a #2
> > > [ 1446.679168] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
> > > [ 1446.680692] Workqueue: kthrotld blk_throtl_dispatch_work_fn
> > > [ 1446.681448] Call Trace:
> > > [ 1446.681800] dump_stack+0x9b/0xce
> > > [ 1446.682259] ? blk_mq_get_driver_tag+0x9a4/0xa90
> > > [ 1446.682916] print_address_description.constprop.6+0x3e/0x60
> > > [ 1446.683688] ? __cpuidle_text_end+0x5/0x5
> > > [ 1446.684239] ? vprintk_func+0x6b/0x120
> > > [ 1446.684748] ? blk_mq_get_driver_tag+0x9a4/0xa90
> > > [ 1446.685373] ? blk_mq_get_driver_tag+0x9a4/0xa90
> > > [ 1446.685999] kasan_report.cold.9+0x22/0x3a
> > > [ 1446.686559] ? blk_mq_get_driver_tag+0x9a4/0xa90
> > > [ 1446.687186] blk_mq_get_driver_tag+0x9a4/0xa90
> > > [ 1446.687785] blk_mq_dispatch_rq_list+0x21a/0x1d40
> > > [ 1446.688427] ? __sbitmap_get_word+0xc3/0xe0
> > > [ 1446.688992] ? blk_mq_dequeue_from_ctx+0x960/0x960
> > > [ 1446.689641] ? _raw_spin_lock+0x7a/0xd0
> > > [ 1446.690164] ? _raw_spin_lock_irq+0xd0/0xd0
> > > [ 1446.690727] ? sbitmap_get_shallow+0x3c9/0x4e0
> > > [ 1446.691329] ? sbitmap_any_bit_set+0x128/0x190
> > > [ 1446.691928] ? kyber_completed_request+0x290/0x290
> > > [ 1446.692576] __blk_mq_do_dispatch_sched+0x394/0x830
> > > [ 1446.693237] ? blk_mq_sched_request_inserted+0x100/0x100
> > > [ 1446.693948] ? __blk_queue_split+0x31d/0x1380
> > > [ 1446.694540] ? blk_integrity_merge_bio+0xc1/0x370
> > > [ 1446.695182] ? ll_back_merge_fn+0x694/0x1490
> > > [ 1446.695758] __blk_mq_sched_dispatch_requests+0x398/0x4f0
> > > [ 1446.696484] ? bio_attempt_back_merge+0x1cc/0x340
> > > [ 1446.697121] ? blk_mq_do_dispatch_ctx+0x570/0x570
> > > [ 1446.697756] ? _raw_spin_lock+0x7a/0xd0
> > > [ 1446.698279] blk_mq_sched_dispatch_requests+0xdf/0x140
> > > [ 1446.698967] __blk_mq_run_hw_queue+0xc0/0x270
> > > [ 1446.699561] __blk_mq_delay_run_hw_queue+0x4cc/0x550
> > > [ 1446.700231] ? kyber_has_work+0x9a/0x140
> > > [ 1446.700760] ? kyber_completed_request+0x290/0x290
> > > [ 1446.701407] blk_mq_run_hw_queue+0x13b/0x2b0
> > > [ 1446.701982] ? kyber_has_work+0x140/0x140
> > > [ 1446.702593] blk_mq_sched_insert_requests+0x1de/0x390
> > > [ 1446.703309] blk_mq_flush_plug_list+0x4b4/0x760
> > > [ 1446.703946] ? blk_mq_insert_requests+0x4b0/0x4b0
> > > [ 1446.704644] ? __bpf_trace_block_bio_complete+0x30/0x30
> > > [ 1446.705408] blk_flush_plug_list+0x2c5/0x480
> > > [ 1446.706026] ? blk_insert_cloned_request+0x460/0x460
> > > [ 1446.706717] ? _raw_spin_lock_irq+0x7b/0xd0
> > > [ 1446.707292] ? _raw_spin_lock_irqsave+0xe0/0xe0
> > > [ 1446.707901] ? set_next_entity+0x235/0x2210
> > > [ 1446.708471] blk_finish_plug+0x55/0xa0
> > > [ 1446.708980] blk_throtl_dispatch_work_fn+0x23b/0x2e0
> > > [ 1446.709653] ? tg_prfill_limit+0x8a0/0x8a0
> > > [ 1446.710216] ? read_word_at_a_time+0xe/0x20
> > > [ 1446.710780] ? strscpy+0x9a/0x320
> > > [ 1446.711236] process_one_work+0x6d4/0xfe0
> > > [ 1446.711778] worker_thread+0x91/0xc80
> > > [ 1446.712281] ? __kthread_parkme+0xb0/0x110
> > > [ 1446.712834] ? process_one_work+0xfe0/0xfe0
> > > [ 1446.713400] kthread+0x32d/0x3f0
> > > [ 1446.713840] ? kthread_park+0x170/0x170
> > > [ 1446.714362] ret_from_fork+0x1f/0x30
> > > [ 1446.714846]
> > > [ 1446.715062] Allocated by task 1:
> > > [ 1446.715509] kasan_save_stack+0x19/0x40
> > > [ 1446.716026] __kasan_kmalloc.constprop.1+0xc1/0xd0
> > > [ 1446.716673] blk_mq_init_tags+0x6d/0x330
> > > [ 1446.717207] blk_mq_alloc_rq_map+0x50/0x1c0
> > > [ 1446.717769] __blk_mq_alloc_map_and_request+0xe5/0x320
> > > [ 1446.718459] blk_mq_alloc_tag_set+0x679/0xdc0
> > > [ 1446.719050] scsi_add_host_with_dma.cold.3+0xa0/0x5db
> > > [ 1446.719736] virtscsi_probe+0x7bf/0xbd0
> > > [ 1446.720265] virtio_dev_probe+0x402/0x6c0
> > > [ 1446.720808] really_probe+0x276/0xde0
> > > [ 1446.721320] driver_probe_device+0x267/0x3d0
> > > [ 1446.721892] device_driver_attach+0xfe/0x140
> > > [ 1446.722491] __driver_attach+0x13a/0x2c0
> > > [ 1446.723037] bus_for_each_dev+0x146/0x1c0
> > > [ 1446.723603] bus_add_driver+0x3fc/0x680
> > > [ 1446.724145] driver_register+0x1c0/0x400
> > > [ 1446.724693] init+0xa2/0xe8
> > > [ 1446.725091] do_one_initcall+0x9e/0x310
> > > [ 1446.725626] kernel_init_freeable+0xc56/0xcb9
> > > [ 1446.726231] kernel_init+0x11/0x198
> > > [ 1446.726714] ret_from_fork+0x1f/0x30
> > > [ 1446.727212]
> > > [ 1446.727433] Freed by task 26992:
> > > [ 1446.727882] kasan_save_stack+0x19/0x40
> > > [ 1446.728420] kasan_set_track+0x1c/0x30
> > > [ 1446.728943] kasan_set_free_info+0x1b/0x30
> > > [ 1446.729517] __kasan_slab_free+0x111/0x160
> > > [ 1446.730084] kfree+0xb8/0x520
> > > [ 1446.730507] blk_mq_free_map_and_requests+0x10b/0x1b0
> > > [ 1446.731206] blk_mq_realloc_hw_ctxs+0x8cb/0x15b0
> > > [ 1446.731844] blk_mq_init_allocated_queue+0x374/0x1380
> > > [ 1446.732540] blk_mq_init_queue_data+0x7f/0xd0
> > > [ 1446.733155] scsi_mq_alloc_queue+0x45/0x170
> > > [ 1446.733730] scsi_alloc_sdev+0x73c/0xb20
> > > [ 1446.734281] scsi_probe_and_add_lun+0x9a6/0x2d90
> > > [ 1446.734916] __scsi_scan_target+0x208/0xc50
> > > [ 1446.735500] scsi_scan_channel.part.3+0x113/0x170
> > > [ 1446.736149] scsi_scan_host_selected+0x25a/0x360
> > > [ 1446.736783] store_scan+0x290/0x2d0
> > > [ 1446.737275] dev_attr_store+0x55/0x80
> > > [ 1446.737782] sysfs_kf_write+0x132/0x190
> > > [ 1446.738313] kernfs_fop_write_iter+0x319/0x4b0
> > > [ 1446.738921] new_sync_write+0x40e/0x5c0
> > > [ 1446.739429] vfs_write+0x519/0x720
> > > [ 1446.739877] ksys_write+0xf8/0x1f0
> > > [ 1446.740332] do_syscall_64+0x2d/0x40
> > > [ 1446.740802] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > > [ 1446.741462]
> > > [ 1446.741670] The buggy address belongs to the object at ffff8880185afd00
> > > [ 1446.741670] which belongs to the cache kmalloc-256 of size 256
> > > [ 1446.743276] The buggy address is located 16 bytes inside of
> > > [ 1446.743276] 256-byte region [ffff8880185afd00, ffff8880185afe00)
> > > [ 1446.744765] The buggy address belongs to the page:
> > > [ 1446.745416] page:ffffea0000616b00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x185ac
> > > [ 1446.746694] head:ffffea0000616b00 order:2 compound_mapcount:0 compound_pincount:0
> > > [ 1446.747719] flags: 0x1fffff80010200(slab|head)
> > > [ 1446.748337] raw: 001fffff80010200 ffffea00006a3208 ffffea000061bf08 ffff88801004f240
> > > [ 1446.749404] raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
> > > [ 1446.750455] page dumped because: kasan: bad access detected
> > > [ 1446.751227]
> > > [ 1446.751445] Memory state around the buggy address:
> > > [ 1446.752102] ffff8880185afc00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > > [ 1446.753090] ffff8880185afc80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > > [ 1446.754079] >ffff8880185afd00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > [ 1446.755065] ^
> > > [ 1446.755589] ffff8880185afd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > > [ 1446.756574] ffff8880185afe00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > > [ 1446.757566] ==================================================================
> > >
> > > Flag 'BLK_MQ_F_TAG_QUEUE_SHARED' will be set if the second device on the
> > > same host initializes it's queue successfully. However, if the second
> > > device failed to allocate memory in blk_mq_alloc_and_init_hctx() from
> > > blk_mq_realloc_hw_ctxs() from blk_mq_init_allocated_queue(),
> > > __blk_mq_free_map_and_rqs() will be called on error path, and if
> > > 'BLK_MQ_TAG_HCTX_SHARED' is not set, 'tag_set->tags' will be freed
> > > while it's still used by the first device.
> > >
> > > Fix the problem by checking if 'tag_set->tag_list' is emptly before
> > > freeing 'tag_set->tag' during queue initialization.
> > >
> > > Fixes: 868f2f0b7206 ("blk-mq: dynamic h/w context count")
> > > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> > > ---
> > > block/blk-mq.c | 12 ++++++++++--
> > > 1 file changed, 10 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/block/blk-mq.c b/block/blk-mq.c
> > > index 3527ee251a85..529ad8c47377 100644
> > > --- a/block/blk-mq.c
> > > +++ b/block/blk-mq.c
> > > @@ -3571,7 +3571,7 @@ static struct blk_mq_hw_ctx *blk_mq_alloc_and_init_hctx(
> > > }
> > > static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
> > > - struct request_queue *q)
> > > + struct request_queue *q)
> > > {
> > > int i, j, end;
> > > struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
> > > @@ -3636,9 +3636,17 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
> > > for (; j < end; j++) {
> > > struct blk_mq_hw_ctx *hctx = hctxs[j];
> > > + bool free_tags = !blk_mq_is_shared_tags(set->flags) &&
> > > + !q->nr_hw_queues && list_empty(&set->tag_list);
> > > if (hctx) {
> > > - __blk_mq_free_map_and_rqs(set, j);
> > > + /*
> > > + * tags should not be freed if other device is using the
> > > + * tagset. q->nr_hw_queues is zero means current
> > > + * function is called from queue initialization.
> > > + */
> > > + if (free_tags)
> > > + __blk_mq_free_map_and_rqs(set, j);
> > > blk_mq_exit_hctx(q, set, hctx, j);
> > > hctxs[j] = NULL;
> > __blk_mq_free_map_and_rqs() isn't supposed to call in
> > blk_mq_realloc_hw_ctxs(), so why can't we simply remove it here?
> __blk_mq_update_nr_hw_queues
> blk_mq_realloc_hw_ctxs
> if (q->nr_hw_queues != set->nr_hw_queues)
> set->nr_hw_queues = prev_nr_hw_queues;
> If 'tag_set' expansion failed, 'set->nr_hw_queues' will fallback previous
> value. So If we don't
> call '__blk_mq_free_map_and_rqs' to release the newly allocated hardware
> context will lead to
> memory leak.
Then the correct way is to move the freeing of extra map_and_tags into
__blk_mq_update_nr_hw_queues() where it is safe and supposed to do such
thing.
Thanks,
Ming