[PATCH 6/6] rq-qos: fix uaf in rq_qos_done_io()

From: Yu Kuai
Date: Thu Sep 23 2021 - 09:37:05 EST

our test report a uaf:

[ 142.925504] ==================================================================
[ 142.929084] BUG: KASAN: use-after-free in __rq_qos_done_bio+0x57/0x90
[ 142.931131] Read of size 8 at addr ffff88810306d858 by task blkdiscard/858
[ 142.933289]
[ 142.933798] CPU: 1 PID: 858 Comm: blkdiscard Not tainted 5.15.0-rc1-00004-g18bc2dec41ab-d4
[ 142.936580] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_0738364
[ 142.939318] Call Trace:
[ 142.939662] ? dump_stack_lvl+0x73/0x9f
[ 142.940197] ? print_address_description.constprop.0+0x2f/0x250
[ 142.941004] ? __rq_qos_done_bio+0x57/0x90
[ 142.941564] ? __rq_qos_done_bio+0x57/0x90
[ 142.942132] ? kasan_report.cold+0x81/0x165
[ 142.942710] ? __rq_qos_done_bio+0x57/0x90
[ 142.943282] ? __asan_load8+0x74/0x110
[ 142.943798] ? __rq_qos_done_bio+0x57/0x90
[ 142.944365] ? bio_endio+0x142/0x430
[ 142.944864] ? submit_bio_checks+0x178/0xef0
[ 142.945456] ? trace_event_raw_event_block_rq_requeue+0x300/0x300
[ 142.946283] ? mempool_alloc+0xe9/0x2f0
[ 142.946812] ? remove_element+0x130/0x130
[ 142.947371] ? init_timer_key+0x83/0x1b0
[ 142.947917] ? submit_bio_noacct+0x86/0x9c0
[ 142.948496] ? blk_queue_enter+0x6d0/0x6d0
[ 142.949066] ? bio_alloc_bioset+0x1b2/0x3a0
[ 142.949649] ? __rcu_read_unlock+0x45/0x370
[ 142.950227] ? bvec_alloc+0x120/0x120
[ 142.950732] ? submit_bio+0x60/0x230
[ 142.951230] ? blk_next_bio+0x4f/0x70
[ 142.951740] ? __blkdev_issue_discard+0x257/0x520
[ 142.952387] ? __blkdev_issue_write_zeroes+0x270/0x270
[ 142.953089] ? bd_abort_claiming+0x70/0x70
[ 142.953652] ? __kasan_check_write+0x20/0x30
[ 142.954236] ? _raw_spin_lock+0xaf/0x130
[ 142.954769] ? _raw_read_lock_bh+0xa0/0xa0
[ 142.955328] ? __get_locked_pte+0x1b3/0x310
[ 142.955897] ? _raw_spin_unlock+0x3b/0x80
[ 142.956444] ? blkdev_issue_discard+0xd3/0x1a0
[ 142.957051] ? blkdev_issue_write_same+0x540/0x540
[ 142.957708] ? _raw_spin_lock+0xaf/0x130
[ 142.958244] ? bd_abort_claiming+0x70/0x70
[ 142.958805] ? wake_up_bit+0x46/0x50
[ 142.959302] ? preempt_count_sub+0x14/0x160
[ 142.959877] ? _raw_spin_unlock+0x3b/0x80
[ 142.960428] ? bd_abort_claiming+0x65/0x70
[ 142.960993] ? blk_ioctl_discard+0x1bd/0x240
[ 142.961582] ? blkdev_bszset+0x1c0/0x1c0
[ 142.962118] ? special_mapping_fault+0x6f/0x200
[ 142.962743] ? __do_fault+0x80/0x410
[ 142.963241] ? blkdev_common_ioctl+0x6c9/0x1190
[ 142.963877] ? ioctl_file_clone+0x110/0x110
[ 142.964457] ? blk_ioctl_discard+0x240/0x240
[ 142.965038] ? copy_page_range+0x2b60/0x2b60
[ 142.965623] ? vfs_getattr_nosec+0x177/0x190
[ 142.966214] ? __ia32_compat_sys_newfstat+0x40/0x40
[ 142.966885] ? blkdev_ioctl+0x180/0x4b0
[ 142.967409] ? blkdev_common_ioctl+0x1190/0x1190
[ 142.968033] ? handle_mm_fault+0x3c2/0x660
[ 142.968590] ? __kasan_check_write+0x20/0x30
[ 142.969172] ? block_ioctl+0x7d/0xa0
[ 142.969666] ? __x64_sys_ioctl+0xd5/0x150
[ 142.970224] ? do_syscall_64+0x35/0x80
[ 142.970733] ? entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 142.971441]
[ 142.971653] Allocated by task 283:
[ 142.972117] kasan_save_stack+0x23/0x60
[ 142.972637] set_alloc_info+0x46/0x70
[ 142.973136] __kasan_kmalloc+0x8d/0xd0
[ 142.973639] kmem_cache_alloc_trace+0x3e7/0x820
[ 142.974254] wbt_init+0x40/0x430
[ 142.974694] wbt_enable_default+0xbb/0x100
[ 142.975248] blk_register_queue+0x216/0x3e0
[ 142.975812] device_add_disk+0x4ac/0x880
[ 142.976358] sd_probe+0x690/0x910
[ 142.976809] really_probe+0x5c3/0x800
[ 142.977306] __driver_probe_device+0x233/0x330
[ 142.977907] driver_probe_device+0x69/0x140
[ 142.978466] __device_attach_driver+0x125/0x210
[ 142.979081] bus_for_each_drv+0x10e/0x1b0
[ 142.979615] __device_attach_async_helper+0x175/0x230
[ 142.980302] async_run_entry_fn+0x7b/0x310
[ 142.980859] process_one_work+0x46a/0xa80
[ 142.981400] worker_thread+0x33d/0x8d0
[ 142.981917] kthread+0x282/0x300
[ 142.982363] ret_from_fork+0x1f/0x30
[ 142.982862]
[ 142.983077] Freed by task 863:
[ 142.983501] kasan_save_stack+0x23/0x60
[ 142.984029] kasan_set_track+0x24/0x40
[ 142.984547] kasan_set_free_info+0x30/0x60
[ 142.985115] __kasan_slab_free+0x137/0x210
[ 142.985678] kfree+0x10b/0x570
[ 142.986106] wbt_exit+0x68/0x80
[ 142.986535] rq_qos_exit+0x5f/0x80
[ 142.987002] blk_cleanup_queue+0xdb/0x250
[ 142.987546] __scsi_remove_device+0xb1/0x2e0
[ 142.988131] scsi_remove_device+0x38/0x60
[ 142.988676] sdev_store_delete+0x73/0x100
[ 142.989230] dev_attr_store+0x40/0x70
[ 142.989730] sysfs_kf_write+0x89/0xc0
[ 142.990233] kernfs_fop_write_iter+0x21d/0x340
[ 142.990839] new_sync_write+0x27e/0x3a0
[ 142.991362] vfs_write+0x46e/0x630
[ 142.991834] ksys_write+0xcd/0x1e0
[ 142.992300] __x64_sys_write+0x46/0x60
[ 142.992814] do_syscall_64+0x35/0x80
[ 142.993311] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 142.994213] The buggy address belongs to the object at ffff88810306d800
[ 142.994213] which belongs to the cache kmalloc-256 of size 256
[ 142.995889] The buggy address is located 88 bytes inside of
[ 142.995889] 256-byte region [ffff88810306d800, ffff88810306d900)
[ 142.997448] The buggy address belongs to the page:
[ 142.998102] page:0000000069471149 refcount:1 mapcount:0 mapping:0000000000000000 index:0xc
[ 142.999372] head:0000000069471149 order:2 compound_mapcount:0 compound_pincount:0
[ 143.000375] flags: 0x2fffff80010200(slab|head|node=0|zone=2|lastcpupid=0x1fffff)
[ 143.001403] raw: 002fffff80010200 0000000000000000 0000000100000001 ffff88810004cb40
[ 143.002455] raw: 0000000000000000 0000000000200020 00000001ffffffff 0000000000000000
[ 143.003477] page dumped because: kasan: bad access detected
[ 143.004222]
[ 143.004433] Memory state around the buggy address:
[ 143.005077] ffff88810306d700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 143.006040] ffff88810306d780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 143.007012] >ffff88810306d800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 143.007981] ^
[ 143.008795] ffff88810306d880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 143.009764] ffff88810306d900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 143.010731] ==================================================================

This is because 'q_usage_counter' will not hold when bio_endio() is
called from error path, thus bio_endio() can concurrent with
blk_cleanup_queue():

t1 t2

bio_endio
rq_qos_done_bio
__rq_qos_done_bio(q->rq_qos, bio)
blk_cleanup_queue
rq_qos_exit
->rq_qos is freed
-> uaf

Thus split the release of rq_qos to blk_release_queue() to fix the
problem.

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
block/blk-iocost.c | 1 -
block/blk-iolatency.c | 1 -
block/blk-ioprio.c | 4 ----
block/blk-rq-qos.c | 8 ++++----
block/blk-sysfs.c | 1 +
block/blk-wbt.c | 1 -
6 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index b4a6c1f70eb0..4698c6127620 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2810,7 +2810,6 @@ static void ioc_rqos_exit(struct rq_qos *rqos)

del_timer_sync(&ioc->timer);
free_percpu(ioc->pcpu_stat);
- kfree(ioc);
}

static void ioc_rqos_free(struct rq_qos *rqos)
diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index f3b8848e6a46..ca227aa1157f 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -645,7 +645,6 @@ static void blkcg_iolatency_exit(struct rq_qos *rqos)

del_timer_sync(&blkiolat->timer);
blkcg_deactivate_policy(rqos->q, &blkcg_policy_iolatency);
- kfree(blkiolat);
}

static void blkcg_iolatency_free(struct rq_qos *rqos)
diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c
index 55338ebee356..6176b869801b 100644
--- a/block/blk-ioprio.c
+++ b/block/blk-ioprio.c
@@ -205,11 +205,7 @@ static void blkcg_ioprio_track(struct rq_qos *rqos, struct request *rq,

static void blkcg_ioprio_exit(struct rq_qos *rqos)
{
- struct blk_ioprio *blkioprio_blkg =
- container_of(rqos, typeof(*blkioprio_blkg), rqos);
-
blkcg_deactivate_policy(rqos->q, &ioprio_policy);
- kfree(blkioprio_blkg);
}

static void blkcg_ioprio_free(struct rq_qos *rqos)
diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c
index bc22d0312765..38b3404df9a7 100644
--- a/block/blk-rq-qos.c
+++ b/block/blk-rq-qos.c
@@ -300,12 +300,12 @@ void rq_qos_wait(struct rq_wait *rqw, void *private_data,

void rq_qos_exit(struct request_queue *q)
{
- blk_mq_debugfs_unregister_queue_rqos(q);
+ struct rq_qos *rqos = q->rq_qos;

- while (q->rq_qos) {
- struct rq_qos *rqos = q->rq_qos;
- q->rq_qos = rqos->next;
+ blk_mq_debugfs_unregister_queue_rqos(q);
+ while (rqos) {
rqos->ops->exit(rqos);
+ rqos = rqos->next;
}
}

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 614d9d47de36..2cbfb7d33066 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -815,6 +815,7 @@ static void blk_release_queue(struct kobject *kobj)
cancel_delayed_work_sync(&hctx->run_work);
}

+ rq_qos_free(q);
blk_exit_queue(q);

blk_queue_free_zone_bitmaps(q);
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 4190453d5e0b..d4314a1396a8 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -691,7 +691,6 @@ static void wbt_exit(struct rq_qos *rqos)

blk_stat_remove_callback(q, rwb->cb);
blk_stat_free_callback(rwb->cb);
- kfree(rwb);
}

static void wbt_free(struct rq_qos *rqos)
--
2.31.1