[syzbot] KASAN: use-after-free Read in create_worker_cb

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syzbot

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Mar 29, 2021, 3:54:15 PMMar 29
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Hello,

syzbot found the following issue on:

HEAD commit: 93129492 Add linux-next specific files for 20210326
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=144509bad00000
kernel config: https://syzkaller.appspot.com/x/.config?x=4c9322cd4e3b7a16
dashboard link: https://syzkaller.appspot.com/bug?extid=099593561bbd1805b839
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=124ce00ed00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1664d5aad00000

The issue was bisected to:

commit 4d004099a668c41522242aa146a38cc4eb59cb1e
Author: Peter Zijlstra <pet...@infradead.org>
Date: Fri Oct 2 09:04:21 2020 +0000

lockdep: Fix lockdep recursion

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12f96b7cd00000
final oops: https://syzkaller.appspot.com/x/report.txt?x=11f96b7cd00000
console output: https://syzkaller.appspot.com/x/log.txt?x=16f96b7cd00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+099593...@syzkaller.appspotmail.com
Fixes: 4d004099a668 ("lockdep: Fix lockdep recursion")

==================================================================
BUG: KASAN: use-after-free in create_worker_cb+0xaa/0xc0 fs/io-wq.c:272
Read of size 8 at addr ffff88801bf150e8 by task syz-executor364/8509

CPU: 0 PID: 8509 Comm: syz-executor364 Not tainted 5.12.0-rc4-next-20210326-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x141/0x1d7 lib/dump_stack.c:120
print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:232
__kasan_report mm/kasan/report.c:399 [inline]
kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:416
create_worker_cb+0xaa/0xc0 fs/io-wq.c:272
task_work_run+0xdd/0x1a0 kernel/task_work.c:143
exit_task_work include/linux/task_work.h:30 [inline]
do_exit+0xbfc/0x2a60 kernel/exit.c:825
do_group_exit+0x125/0x310 kernel/exit.c:922
__do_sys_exit_group kernel/exit.c:933 [inline]
__se_sys_exit_group kernel/exit.c:931 [inline]
__x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x447359
Code: Unable to access opcode bytes at RIP 0x44732f.
RSP: 002b:00007ffdfb4e3ea8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00000000004b8390 RCX: 0000000000447359
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffffffffffc0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004b8390
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001

Allocated by task 8509:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:428 [inline]
____kasan_kmalloc mm/kasan/common.c:507 [inline]
____kasan_kmalloc mm/kasan/common.c:466 [inline]
__kasan_kmalloc+0x9b/0xd0 mm/kasan/common.c:516
kmalloc_node include/linux/slab.h:574 [inline]
kzalloc_node include/linux/slab.h:697 [inline]
io_wq_create+0x6e4/0xca0 fs/io-wq.c:934
io_init_wq_offload fs/io_uring.c:7938 [inline]
io_uring_alloc_task_context+0x1bf/0x660 fs/io_uring.c:7957
__io_uring_add_task_file+0x29a/0x3c0 fs/io_uring.c:8915
io_uring_add_task_file fs/io_uring.c:8951 [inline]
io_uring_install_fd fs/io_uring.c:9509 [inline]
io_uring_create fs/io_uring.c:9656 [inline]
io_uring_setup+0x20dd/0x2b00 fs/io_uring.c:9693
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 8509:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:357
____kasan_slab_free mm/kasan/common.c:360 [inline]
____kasan_slab_free mm/kasan/common.c:325 [inline]
__kasan_slab_free+0xfb/0x130 mm/kasan/common.c:368
kasan_slab_free include/linux/kasan.h:212 [inline]
slab_free_hook mm/slub.c:1578 [inline]
slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1603
slab_free mm/slub.c:3163 [inline]
kfree+0xe5/0x7f0 mm/slub.c:4230
io_wq_destroy+0x13e/0x2d0 fs/io-wq.c:1022
io_wq_put fs/io-wq.c:1032 [inline]
io_wq_put_and_exit+0x7a/0xa0 fs/io-wq.c:1038
io_uring_clean_tctx+0xed/0x160 fs/io_uring.c:8988
__io_uring_files_cancel+0x703/0x850 fs/io_uring.c:9053
io_uring_files_cancel include/linux/io_uring.h:22 [inline]
do_exit+0x299/0x2a60 kernel/exit.c:780
do_group_exit+0x125/0x310 kernel/exit.c:922
__do_sys_exit_group kernel/exit.c:933 [inline]
__se_sys_exit_group kernel/exit.c:931 [inline]
__x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff88801bf15000
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 232 bytes inside of
1024-byte region [ffff88801bf15000, ffff88801bf15400)
The buggy address belongs to the page:
page:ffffea00006fc400 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88801bf15800 pfn:0x1bf10
head:ffffea00006fc400 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea00004cd808 ffff888010840888 ffff888010841dc0
raw: ffff88801bf15800 000000000010000d 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88801bf14f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88801bf15000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88801bf15080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88801bf15100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88801bf15180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This report is generated by a bot. It may contain errors.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

Jens Axboe

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Mar 29, 2021, 3:56:45 PMMar 29
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#syz test: git://git.kernel.dk/linux-block for-5.13/io_uring

--
Jens Axboe

syzbot

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Mar 29, 2021, 7:33:09 PMMar 29
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Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+099593...@syzkaller.appspotmail.com

Tested on:

commit: 24996dbd io_uring: reg buffer overflow checks hardening
git tree: git://git.kernel.dk/linux-block for-5.13/io_uring
kernel config: https://syzkaller.appspot.com/x/.config?x=cbb3af9ca0d22f7a
dashboard link: https://syzkaller.appspot.com/bug?extid=099593561bbd1805b839
compiler:

Note: testing is done by a robot and is best-effort only.
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