On Fri, Sep 24, 2021 at 09:23:42AM +0800, yukuai (C) wrote:
> On 2021/09/24 8:41, Ming Lei wrote:
> > On Thu, Sep 23, 2021 at 09:46:31PM +0800, Yu Kuai wrote:
> > > 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():
> >
> > What is the exact error path? We actually grabs one ref of q_usage_counter
> > during submitting bio, so the issue should have been fixed by not
> > releasing the refcount early in the error path? Or the refcnt isn't grabbed
> > yet when handling the error?
> >
>
> Hi,
>
> We found at least two places:
>
> The first is error path from submit_bio_checks(), and we succeed to
> construct repoducer here.
>
> The second is from bio_queue_enter(), bio_endio() will be called if
> blk_queue_enter() failed.
OK, both should be addressed by the following simple patch:
diff --git a/block/bio.c b/block/bio.c
index 5df3dd282e40..a6fb6a0b4295 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1466,7 +1466,7 @@ void bio_endio(struct bio *bio)
if (!bio_integrity_endio(bio))
return;
- if (bio->bi_bdev)
+ if (bio->bi_bdev && bio_flagged(bio, BIO_TRACKED))
rq_qos_done_bio(bio->bi_bdev->bd_disk->queue, bio);
if (bio->bi_bdev && bio_flagged(bio, BIO_TRACE_COMPLETION)) {
--
Ming
