KASAN: use-after-free Read in blk_mq_free_rqs

From: syzbot
Date: Thu Jun 06 2019 - 14:46:18 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 9221dced Merge tag 'for-linus-20190601' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16b3b772a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=1fa7e451a5cac069
dashboard link: https://syzkaller.appspot.com/bug?extid=784281a934c3f71eb71a
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=149089aaa00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11b24edea00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+784281a934c3f71eb71a@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: use-after-free in blk_mq_free_rqs+0x49f/0x4b0 block/blk-mq.c:2049
Read of size 8 at addr ffff88809b5c0b10 by task kworker/1:1/22

CPU: 1 PID: 22 Comm: kworker/1:1 Not tainted 5.2.0-rc2+ #17
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events __blk_release_queue
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0x7c/0x20d mm/kasan/report.c:188
__kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
kasan_report+0x12/0x20 mm/kasan/common.c:614
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
blk_mq_free_rqs+0x49f/0x4b0 block/blk-mq.c:2049
blk_mq_sched_free_tags block/blk-mq-sched.c:453 [inline]
blk_mq_sched_tags_teardown+0x126/0x210 block/blk-mq-sched.c:485
blk_mq_exit_sched+0x1fa/0x2d0 block/blk-mq-sched.c:557
elevator_exit+0x70/0xa0 block/elevator.c:185
blk_exit_queue block/blk-sysfs.c:853 [inline]
__blk_release_queue+0x127/0x330 block/blk-sysfs.c:895
process_one_work+0x989/0x1790 kernel/workqueue.c:2269
worker_thread+0x98/0xe40 kernel/workqueue.c:2415
kthread+0x354/0x420 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 8904:
save_stack+0x23/0x90 mm/kasan/common.c:71
set_track mm/kasan/common.c:79 [inline]
__kasan_kmalloc mm/kasan/common.c:489 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:462
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:503
kmem_cache_alloc_trace+0x151/0x750 mm/slab.c:3555
kmalloc include/linux/slab.h:547 [inline]
kzalloc include/linux/slab.h:742 [inline]
loop_add+0x51/0x8d0 drivers/block/loop.c:1973
loop_control_ioctl drivers/block/loop.c:2157 [inline]
loop_control_ioctl+0x165/0x360 drivers/block/loop.c:2139
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0xd5f/0x1380 fs/ioctl.c:696
ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8905:
save_stack+0x23/0x90 mm/kasan/common.c:71
set_track mm/kasan/common.c:79 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:451
kasan_slab_free+0xe/0x10 mm/kasan/common.c:459
__cache_free mm/slab.c:3432 [inline]
kfree+0xcf/0x220 mm/slab.c:3755
loop_remove+0xa1/0xd0 drivers/block/loop.c:2078
loop_control_ioctl drivers/block/loop.c:2173 [inline]
loop_control_ioctl+0x320/0x360 drivers/block/loop.c:2139
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0xd5f/0x1380 fs/ioctl.c:696
ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88809b5c0900
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 528 bytes inside of
1024-byte region [ffff88809b5c0900, ffff88809b5c0d00)
The buggy address belongs to the page:
page:ffffea00026d7000 refcount:1 mapcount:0 mapping:ffff8880aa400ac0 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea0002411188 ffffea000290c088 ffff8880aa400ac0
raw: 0000000000000000 ffff88809b5c0000 0000000100000007 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88809b5c0a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809b5c0a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

ffff88809b5c0b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

^
ffff88809b5c0b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809b5c0c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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Next message: Tim Chen: "[PATCH v2] Documentation: Add section about CPU vulnerabilities for Spectre"
Previous message: Sean Christopherson: "Re: [PATCH] KVM: nVMX: Rename prepare_vmcs02_*_full to prepare_vmcs02_*_extra"
Next in thread: Ming Lei: "Re: KASAN: use-after-free Read in blk_mq_free_rqs"
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