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

[Ming Lei]

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?


Thanks,
Ming