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Subjectuse-after-free in bfq_idle_slice_timer()
Hi,

we have seen the attached use-after-free in bfq_idle_slice_timer()
while running reboot tests. The code in these tests includes all
bfq patches up to and including commit eed47d19d936 ("block, bfq:
fix use after free in bfq_bfqq_expire").

gdb points to the dereference of struct bfq_queue *bfqq in
bfq_bfqq_budget_timeout(). My suspicion is that the cleanup path
in bfq_put_queue() may not clear bfqd->in_service_queue, but I don't
understand the code well enough to be sure.

Any thoughts / comments ?

Thanks,
Guenter

---
[ 25.307269] ==================================================================
[ 25.314555] BUG: KASAN: use-after-free in bfq_idle_slice_timer+0x88/0x1d4
[ 25.321359] Read of size 8 at addr fffffff089360440 by task swapper/0/0
[ 25.327975]
[ 25.329487] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G S 4.19.38 #37
[ 25.336974] Hardware name: <...> rev2 board (DT)
[ 25.342378] Call trace:
[ 25.344844] dump_backtrace+0x0/0x358
[ 25.348521] show_stack+0x20/0x2c
[ 25.351849] dump_stack+0x130/0x19c
[ 25.355353] print_address_description+0x74/0x250
[ 25.360068] kasan_report+0x27c/0x2a0
[ 25.363742] __asan_report_load8_noabort+0x2c/0x38
[ 25.368546] bfq_idle_slice_timer+0x88/0x1d4
[ 25.372829] __hrtimer_run_queues+0x794/0xa34
[ 25.377197] hrtimer_interrupt+0x278/0x600
[ 25.381310] arch_timer_handler_phys+0x5c/0x6c
[ 25.385767] handle_percpu_devid_irq+0x2e4/0x754
[ 25.390399] __handle_domain_irq+0xd4/0x158
[ 25.394593] gic_handle_irq+0x208/0x260
[ 25.398437] el1_irq+0xb0/0x128
[ 25.401591] arch_cpu_idle+0x20c/0x548
[ 25.405352] do_idle+0x184/0x4dc
[ 25.408590] cpu_startup_entry+0x24/0x28
[ 25.412526] rest_init+0x114/0x148
[ 25.415939] start_kernel+0x4c8/0x5c4
[ 25.419605]
[ 25.421105] Allocated by task 1430:
[ 25.424606] kasan_kmalloc+0xe0/0x1ac
[ 25.428279] kasan_slab_alloc+0x14/0x1c
[ 25.432127] kmem_cache_alloc+0x178/0x278
[ 25.436149] bfq_get_queue+0x160/0x650
[ 25.439911] bfq_get_bfqq_handle_split+0xcc/0x2fc
[ 25.444627] bfq_init_rq+0x254/0x18c0
[ 25.448301] bfq_insert_requests+0x5d0/0x1048
[ 25.452669] blk_mq_sched_insert_requests+0x130/0x204
[ 25.457734] blk_mq_flush_plug_list+0x844/0x91c
[ 25.462278] blk_flush_plug_list+0x3e4/0x778
[ 25.466559] blk_finish_plug+0x54/0x78
[ 25.470322] read_pages+0x294/0x2f0
[ 25.473824] __do_page_cache_readahead+0x1a4/0x354
[ 25.478628] filemap_fault+0x8ec/0xbb4
[ 25.482389] ext4_filemap_fault+0x84/0xa4
[ 25.486409] __do_fault+0x128/0x338
[ 25.489909] handle_mm_fault+0x1de0/0x2588
[ 25.494017] do_page_fault+0x464/0x8d8
[ 25.497777] do_translation_fault+0x6c/0x88
[ 25.501969] do_mem_abort+0xd8/0x2d0
[ 25.505554] do_el0_ia_bp_hardening+0x13c/0x1a8
[ 25.510094] el0_ia+0x18/0x1c
[ 25.513065]
[ 25.514562] Freed by task 1430:
[ 25.517715] __kasan_slab_free+0x13c/0x21c
[ 25.521821] kasan_slab_free+0x10/0x1c
[ 25.525582] kmem_cache_free+0x7c/0x5f8
[ 25.529429] bfq_put_queue+0x19c/0x2e4
[ 25.533191] bfq_exit_icq_bfqq+0x108/0x228
[ 25.537299] bfq_exit_icq+0x20/0x38
[ 25.540798] ioc_exit_icq+0xe4/0x16c
[ 25.544384] put_io_context_active+0x174/0x234
[ 25.548836] exit_io_context+0x84/0x94
[ 25.552599] do_exit+0x13b4/0x18e4
[ 25.556013] do_group_exit+0x1cc/0x204
[ 25.559775] __wake_up_parent+0x0/0x5c
[ 25.563537] __se_sys_exit_group+0x0/0x24
[ 25.567558] el0_svc_common+0x124/0x1ec
[ 25.571407] el0_svc_compat_handler+0x84/0xb0
[ 25.575774] el0_svc_compat+0x8/0x18
[ 25.579351]
[ 25.580854] The buggy address belongs to the object at fffffff089360338
[ 25.580854] which belongs to the cache bfq_queue of size 464
[ 25.587350] cros-ec-spi spi2.0: SPI transfer timed out
[ 25.593209] The buggy address is located 264 bytes inside of
[ 25.593209] 464-byte region [fffffff089360338, fffffff089360508)
[ 25.593216] The buggy address belongs to the page:
[ 25.593234] page:ffffffbfc224d800 count:1 mapcount:0 mapping:fffffff09916d880 index:0xfffffff089360cc8
[ 25.598388] cros-ec-spi spi2.0: spi transfer failed: -110
[ 25.610092] compound_mapcount: 0
[ 25.610109] flags: 0x4000000000008100(slab|head)
[ 25.610133] raw: 4000000000008100 ffffffbfc14c1908 fffffff0991668a0 fffffff09916d880
[ 25.615021] cros-ec-spi spi2.0: Command xfer error (err:-110)
[ 25.624225] raw: fffffff089360cc8 000000000014000d 00000001ffffffff 0000000000000000
[ 25.624233] page dumped because: kasan: bad access detected
[ 25.624237]
[ 25.624243] Memory state around the buggy address:
[ 25.624257] fffffff089360300: fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb fb
[ 25.624271] fffffff089360380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 25.630223] cros-ec-i2c-tunnel 11012000.spi:ec@0:i2c-tunnel: Error transferring EC i2c message -110
[ 25.632977] >fffffff089360400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 25.632985] ^
[ 25.632997] fffffff089360480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 25.633010] fffffff089360500: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 25.633016] ==================================================================

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