[syzbot] [io-uring?] WARNING: refcount bug in io_send_zc_cleanup (2)

[syzbot] [io-uring?] WARNING: refcount bug in io_send_zc_cleanup (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    d07de43e3f05 Merge tag 'io_uring-6.14-20250321' of git://g..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=14223004580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=620facf12ff15d10
dashboard link: https://syzkaller.appspot.com/bug?extid=cf285a028ffba71b2ef5
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16be1c4c580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12223004580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a241563b93db/disk-d07de43e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6c435395db14/vmlinux-d07de43e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/59fc4b510cae/bzImage-d07de43e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cf285a028ffba71b2ef5@syzkaller.appspotmail.com

------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 5823 at lib/refcount.c:28 refcount_warn_saturate+0x15a/0x1d0 lib/refcount.c:28
Modules linked in:
CPU: 0 UID: 0 PID: 5823 Comm: syz-executor232 Not tainted 6.14.0-rc7-syzkaller-00186-gd07de43e3f05 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:refcount_warn_saturate+0x15a/0x1d0 lib/refcount.c:28
Code: c0 e1 7f 8c e8 d7 bc 93 fc 90 0f 0b 90 90 eb 99 e8 6b 01 d4 fc c6 05 97 15 38 0b 01 90 48 c7 c7 20 e2 7f 8c e8 b7 bc 93 fc 90 <0f> 0b 90 90 e9 76 ff ff ff e8 48 01 d4 fc c6 05 71 15 38 0b 01 90
RSP: 0018:ffffc90003e8f9c0 EFLAGS: 00010246
RAX: bae32b5aa58f9a00 RBX: ffff88807f4ad8d0 RCX: ffff888034e08000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: ffffffff81819d62 R09: fffffbfff1d3a69c
R10: dffffc0000000000 R11: fffffbfff1d3a69c R12: dffffc0000000000
R13: 1ffff11005aa3f80 R14: 1ffff1100fe95af6 R15: ffff88807f4ad7b0
FS:  000055557c8ba480(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000000022c CR3: 000000003574c000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 io_notif_flush io_uring/notif.h:40 [inline]
 io_send_zc_cleanup+0x121/0x170 io_uring/net.c:1222
 io_clean_op+0x58c/0x9a0 io_uring/io_uring.c:406
 io_free_batch_list io_uring/io_uring.c:1429 [inline]
 __io_submit_flush_completions+0xc16/0xd20 io_uring/io_uring.c:1470
 io_submit_flush_completions io_uring/io_uring.h:159 [inline]
 ctx_flush_and_put io_uring/io_uring.c:1031 [inline]
 io_handle_tw_list+0x473/0x500 io_uring/io_uring.c:1071
 tctx_task_work_run+0x9a/0x370 io_uring/io_uring.c:1123
 tctx_task_work+0x9a/0x100 io_uring/io_uring.c:1141
 task_work_run+0x24f/0x310 kernel/task_work.c:227
 ptrace_notify+0x2d9/0x380 kernel/signal.c:2522
 ptrace_report_syscall include/linux/ptrace.h:415 [inline]
 ptrace_report_syscall_exit include/linux/ptrace.h:477 [inline]
 syscall_exit_work+0xc7/0x1d0 kernel/entry/common.c:173
 syscall_exit_to_user_mode_prepare kernel/entry/common.c:200 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:205 [inline]
 syscall_exit_to_user_mode+0x24a/0x340 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fda97775569
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe9ef18ea8 EFLAGS: 00000216 ORIG_RAX: 00000000000001aa
RAX: 0000000000001000 RBX: 0000000000000007 RCX: 00007fda97775569
RDX: 0000000000000000 RSI: 00000000000047bc RDI: 0000000000000007
RBP: 0000200000000480 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000021 R11: 0000000000000216 R12: 000000000000081f
R13: 00002000000000c0 R14: 0000000000000001 R15: 0000000000000001
 </TASK>


---
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Re: [syzbot] [io-uring?] WARNING: refcount bug in io_send_zc_cleanup (2)

[Pavel Begunkov]

On 3/22/25 07:06, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    d07de43e3f05 Merge tag 'io_uring-6.14-20250321' of git://g..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=14223004580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=620facf12ff15d10
> dashboard link: https://syzkaller.appspot.com/bug?extid=cf285a028ffba71b2ef5
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16be1c4c580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12223004580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/a241563b93db/disk-d07de43e.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6c435395db14/vmlinux-d07de43e.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/59fc4b510cae/bzImage-d07de43e.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+cf285a028ffba71b2ef5@syzkaller.appspotmail.com

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


-- 
Pavel Begunkov

Re: [syzbot] [io-uring?] WARNING: refcount bug in io_send_zc_cleanup (2)

[syzbot]

Hello,

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

Reported-by: syzbot+cf285a028ffba71b2ef5@syzkaller.appspotmail.com
Tested-by: syzbot+cf285a028ffba71b2ef5@syzkaller.appspotmail.com

Tested on:

commit:         e1306007 io_uring/net: fix sendzc double notif flush
git tree:       https://github.com/isilence/linux.git syz/sendzc-cleanup
console output: https://syzkaller.appspot.com/x/log.txt?x=15809c4c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6fa548b75e783182
dashboard link: https://syzkaller.appspot.com/bug?extid=cf285a028ffba71b2ef5
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [io-uring?] WARNING: refcount bug in io_send_zc_cleanup (2)

[syzbot]

syzbot has bisected this issue to:

commit cc34d8330e036b6bffa88db9ea537bae6b03948f
Author: Jens Axboe <axboe@kernel.dk>
Date:   Thu Mar 20 18:25:12 2025 +0000

    io_uring/net: don't clear REQ_F_NEED_CLEANUP unconditionally

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15ef043f980000
start commit:   d07de43e3f05 Merge tag 'io_uring-6.14-20250321' of git://g..
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=17ef043f980000
console output: https://syzkaller.appspot.com/x/log.txt?x=13ef043f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=620facf12ff15d10
dashboard link: https://syzkaller.appspot.com/bug?extid=cf285a028ffba71b2ef5
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16be1c4c580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12223004580000

Reported-by: syzbot+cf285a028ffba71b2ef5@syzkaller.appspotmail.com
Fixes: cc34d8330e03 ("io_uring/net: don't clear REQ_F_NEED_CLEANUP unconditionally")

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