[syzbot] KASAN: use-after-free Write in __io_free_req

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: bdcc9f6a5682 Add linux-next specific files for 20211029
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12a87e22b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=cea91ee10b0cd274
dashboard link: https://syzkaller.appspot.com/bug?extid=78b76ebc91042904f34e
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10cf03e2b00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+78b76e...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in wq_list_add_head fs/io-wq.h:71 [inline]
BUG: KASAN: use-after-free in __io_free_req+0x33f/0x3c5 fs/io_uring.c:2040
Write of size 8 at addr ffff8880713ecbb8 by task syz-executor.0/8059

CPU: 1 PID: 8059 Comm: syz-executor.0 Not tainted 5.15.0-rc7-next-20211029-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247
__kasan_report mm/kasan/report.c:433 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:450
wq_list_add_head fs/io-wq.h:71 [inline]
__io_free_req+0x33f/0x3c5 fs/io_uring.c:2040
tctx_task_work+0x1b3/0x630 fs/io_uring.c:2207
task_work_run+0xdd/0x1a0 kernel/task_work.c:164
exit_task_work include/linux/task_work.h:32 [inline]
do_exit+0xc14/0x2b40 kernel/exit.c:832
do_group_exit+0x125/0x310 kernel/exit.c:929
get_signal+0x47d/0x21d0 kernel/signal.c:2820
arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
handle_signal_work kernel/entry/common.c:148 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f9da8c4ea39
Code: Unable to access opcode bytes at RIP 0x7f9da8c4ea0f.
RSP: 002b:00007f9da83a3218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f9da8d62028 RCX: 00007f9da8c4ea39
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f9da8d62028
RBP: 00007f9da8d62020 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f9da8d6202c
R13: 00007ffd6e91741f R14: 00007f9da83a3300 R15: 0000000000022000
</TASK>

Allocated by task 8059:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:46 [inline]
set_alloc_info mm/kasan/common.c:434 [inline]
__kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:467
kasan_slab_alloc include/linux/kasan.h:259 [inline]
slab_post_alloc_hook mm/slab.h:519 [inline]
kmem_cache_alloc_bulk+0x39d/0x720 mm/slub.c:3730
__io_alloc_req_refill fs/io_uring.c:1977 [inline]
io_alloc_req_refill fs/io_uring.c:2003 [inline]
io_submit_sqes.cold+0x20b/0x43d fs/io_uring.c:7325
__do_sys_io_uring_enter+0xf6e/0x1f50 fs/io_uring.c:10052
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 1041:
kasan_save_stack+0x1e/0x50 mm/kasan/common.c:38
kasan_set_track+0x21/0x30 mm/kasan/common.c:46
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
____kasan_slab_free mm/kasan/common.c:366 [inline]
____kasan_slab_free mm/kasan/common.c:328 [inline]
__kasan_slab_free+0xff/0x130 mm/kasan/common.c:374
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:1723 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1749
slab_free mm/slub.c:3513 [inline]
kmem_cache_free+0x92/0x5e0 mm/slub.c:3529
io_req_caches_free+0x1aa/0x1e6 fs/io_uring.c:9291
io_ring_exit_work+0x1e4/0xbe8 fs/io_uring.c:9467
process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298
worker_thread+0x658/0x11f0 kernel/workqueue.c:2445
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the object at ffff8880713ecb40
which belongs to the cache io_kiocb of size 224
The buggy address is located 120 bytes inside of
224-byte region [ffff8880713ecb40, ffff8880713ecc20)
The buggy address belongs to the page:
page:ffffea0001c4fb00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880713ec8c0 pfn:0x713ec
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea0001c4d400 dead000000000004 ffff88814607bdc0
raw: ffff8880713ec8c0 00000000800c000b 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 7168, ts 1580559391621, free_ts 1580537948913
prep_new_page mm/page_alloc.c:2418 [inline]
get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4149
__alloc_pages+0x1b2/0x500 mm/page_alloc.c:5369
alloc_pages+0x1a7/0x300 mm/mempolicy.c:2191
alloc_slab_page mm/slub.c:1793 [inline]
allocate_slab mm/slub.c:1930 [inline]
new_slab+0x32d/0x4a0 mm/slub.c:1993
___slab_alloc+0x918/0xfe0 mm/slub.c:3022
kmem_cache_alloc_bulk+0x21a/0x720 mm/slub.c:3706
__io_alloc_req_refill fs/io_uring.c:1977 [inline]
io_alloc_req_refill fs/io_uring.c:2003 [inline]
io_submit_sqes.cold+0x20b/0x43d fs/io_uring.c:7325
__do_sys_io_uring_enter+0xf6e/0x1f50 fs/io_uring.c:10052
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1338 [inline]
free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1389
free_unref_page_prepare mm/page_alloc.c:3309 [inline]
free_unref_page_list+0x1a9/0xfa0 mm/page_alloc.c:3425
release_pages+0x3f4/0x1480 mm/swap.c:979
tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
tlb_flush_mmu_free mm/mmu_gather.c:242 [inline]
tlb_flush_mmu mm/mmu_gather.c:249 [inline]
tlb_finish_mmu+0x165/0x8c0 mm/mmu_gather.c:340
exit_mmap+0x1ea/0x630 mm/mmap.c:3173
__mmput+0x122/0x4b0 kernel/fork.c:1164
mmput+0x56/0x60 kernel/fork.c:1185
exit_mm kernel/exit.c:507 [inline]
do_exit+0xb27/0x2b40 kernel/exit.c:819
do_group_exit+0x125/0x310 kernel/exit.c:929
get_signal+0x47d/0x21d0 kernel/signal.c:2820
arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
handle_signal_work kernel/entry/common.c:148 [inline]
exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae

Memory state around the buggy address:
ffff8880713eca80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
ffff8880713ecb00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>ffff8880713ecb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880713ecc00: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880713ecc80: 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.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Pavel Begunkov]

On 10/29/21 15:34, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: bdcc9f6a5682 Add linux-next specific files for 20211029
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=12a87e22b00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=cea91ee10b0cd274
> dashboard link: https://syzkaller.appspot.com/bug?extid=78b76ebc91042904f34e
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10cf03e2b00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+78b76e...@syzkaller.appspotmail.com

#syz test: git://git.kernel.dk/linux-block for-5.16/io_uring

--
Pavel Begunkov

[Pavel Begunkov]

On 10/29/21 15:34, syzbot wrote:

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: bdcc9f6a5682 Add linux-next specific files for 20211029
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=12a87e22b00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=cea91ee10b0cd274
> dashboard link: https://syzkaller.appspot.com/bug?extid=78b76ebc91042904f34e
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10cf03e2b00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+78b76e...@syzkaller.appspotmail.com

#syz test: git://git.kernel.dk/linux-block 3884b83dff245e41def99ceacca8ed2056baf0a8

--
Pavel Begunkov

[Pavel Begunkov]

On 10/29/21 15:45, Pavel Begunkov wrote:
> On 10/29/21 15:34, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    bdcc9f6a5682 Add linux-next specific files for 20211029
>> git tree:       linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=12a87e22b00000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=cea91ee10b0cd274
>> dashboard link: https://syzkaller.appspot.com/bug?extid=78b76ebc91042904f34e
>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10cf03e2b00000
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+78b76e...@syzkaller.appspotmail.com
>
> #syz test: git://git.kernel.dk/linux-block for-5.16/io_uring

#syz test: git://git.kernel.dk/linux-block 3ecd20a9c77c632a5afe4e134781e1629936adab

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+78b76e...@syzkaller.appspotmail.com

Tested on:

commit: 1d5f5ea7 io-wq: remove worker to owner tw dependency
git tree: git://git.kernel.dk/linux-block for-5.16/io_uring
kernel config: https://syzkaller.appspot.com/x/.config?x=10c050a45aafafcc

dashboard link: https://syzkaller.appspot.com/bug?extid=78b76ebc91042904f34e
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

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

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+78b76e...@syzkaller.appspotmail.com

Tested on:

commit: 3884b83d io_uring: don't assign write hint in the read..
git tree: git://git.kernel.dk/linux-block
kernel config: https://syzkaller.appspot.com/x/.config?x=10c050a45aafafcc

dashboard link: https://syzkaller.appspot.com/bug?extid=78b76ebc91042904f34e
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

failed to checkout kernel repo git://git.kernel.dk/linux-block on commit 3ecd20a9c77c632a5afe4e134781e1629936adab: failed to run ["git" "checkout" "3ecd20a9c77c632a5afe4e134781e1629936adab"]: exit status 128
fatal: reference is not a tree: 3ecd20a9c77c632a5afe4e134781e1629936adab



Tested on:

commit: [unknown
git tree: git://git.kernel.dk/linux-block 3ecd20a9c77c632a5afe4e134781e1629936adab

[Pavel Begunkov]

On 10/29/21 22:12, syzbot wrote:
> Hello,
>
> syzbot tried to test the proposed patch but the build/boot failed:
>
> failed to checkout kernel repo git://git.kernel.dk/linux-block on commit 3ecd20a9c77c632a5afe4e134781e1629936adab: failed to run ["git" "checkout" "3ecd20a9c77c632a5afe4e134781e1629936adab"]: exit status 128
> fatal: reference is not a tree: 3ecd20a9c77c632a5afe4e134781e1629936adab

#syz test: https://github.com/isilence/linux.git syz-test-iofree

>
> Tested on:
>
> commit: [unknown
> git tree: git://git.kernel.dk/linux-block 3ecd20a9c77c632a5afe4e134781e1629936adab
> dashboard link: https://syzkaller.appspot.com/bug?extid=78b76ebc91042904f34e
> compiler:
>

--
Pavel Begunkov

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING: refcount bug in delayed_put_task_struct

------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 19 at lib/refcount.c:28 refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
Modules linked in:
CPU: 1 PID: 19 Comm: ksoftirqd/1 Not tainted 5.15.0-rc6-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

RIP: 0010:refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
Code: e9 db fe ff ff 48 89 df e8 7c aa 1a fe e9 8a fe ff ff e8 92 6c d3 fd 48 c7 c7 80 bb be 89 c6 05 95 a4 8d 09 01 e8 5b 36 19 05 <0f> 0b e9 af fe ff ff 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 55
RSP: 0018:ffffc90000d97d00 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888011af5580 RSI: ffffffff815e8868 RDI: fffff520001b2f92
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815e260e R11: 0000000000000000 R12: ffff888071c45580
R13: ffff888071c455a8 R14: 0000000000000004 R15: ffff888071c46a50
FS: 0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe200c24218 CR3: 000000006f2d8000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__refcount_sub_and_test include/linux/refcount.h:283 [inline]
__refcount_dec_and_test include/linux/refcount.h:315 [inline]
refcount_dec_and_test include/linux/refcount.h:333 [inline]
put_task_struct include/linux/sched/task.h:112 [inline]
delayed_put_task_struct+0x2e3/0x340 kernel/exit.c:172
rcu_do_batch kernel/rcu/tree.c:2508 [inline]
rcu_core+0x7ab/0x1470 kernel/rcu/tree.c:2743
__do_softirq+0x29b/0x9c2 kernel/softirq.c:558
run_ksoftirqd kernel/softirq.c:920 [inline]
run_ksoftirqd+0x2d/0x60 kernel/softirq.c:912
smpboot_thread_fn+0x645/0x9c0 kernel/smpboot.c:164
kthread+0x3e5/0x4d0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295


Tested on:

commit: 3ecd20a9 io-wq: remove worker to owner tw dependency
git tree: https://github.com/isilence/linux.git syz-test-iofree
console output: https://syzkaller.appspot.com/x/log.txt?x=160209d4b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=10c050a45aafafcc
dashboard link: https://syzkaller.appspot.com/bug?extid=78b76ebc91042904f34e

[Pavel Begunkov]

On 10/29/21 15:34, syzbot wrote:

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: bdcc9f6a5682 Add linux-next specific files for 20211029
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=12a87e22b00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=cea91ee10b0cd274
> dashboard link: https://syzkaller.appspot.com/bug?extid=78b76ebc91042904f34e
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10cf03e2b00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+78b76e...@syzkaller.appspotmail.com

Hey Xiaoguang,

Apparently, this was caused by those 3 dropped poll patches, when you'll
be resending would be great if you test with this syz repro as well.

--
Pavel Begunkov

[syzbot]

syzbot has bisected this issue to:

commit 34ced75ca1f63fac6148497971212583aa0f7a87
Author: Xiaoguang Wang <xiaogua...@linux.alibaba.com>
Date: Mon Oct 25 05:38:48 2021 +0000

io_uring: reduce frequent add_wait_queue() overhead for multi-shot poll request

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14f83bbab00000
start commit: bdcc9f6a5682 Add linux-next specific files for 20211029
git tree: linux-next
final oops: https://syzkaller.appspot.com/x/report.txt?x=16f83bbab00000
console output: https://syzkaller.appspot.com/x/log.txt?x=12f83bbab00000

kernel config: https://syzkaller.appspot.com/x/.config?x=cea91ee10b0cd274
dashboard link: https://syzkaller.appspot.com/bug?extid=78b76ebc91042904f34e

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10cf03e2b00000

Reported-by: syzbot+78b76e...@syzkaller.appspotmail.com
Fixes: 34ced75ca1f6 ("io_uring: reduce frequent add_wait_queue() overhead for multi-shot poll request")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.