Re: [syzbot] WARNING in __percpu_ref_exit (2)

syzbot suspects this issue was fixed by commit:

commit 43016d02cf6e46edfc4696452251d34bba0c0435
Author: Florian Westphal [off-list ref]
Date:   Mon May 3 11:51:15 2021 +0000

    netfilter: arptables: use pernet ops struct during unregister

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10acd273300000
start commit:   c98ff1d013d2 Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=1c70e618af4c2e92
dashboard link: https://syzkaller.appspot.com/bug?extid=d6218cb2fae0b2411e9d
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=145cb2b6d00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=157b72b1d00000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: netfilter: arptables: use pernet ops struct during unregister

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

On Mon, 13 Sept 2021 at 11:22, syzbot
[off-list ref] wrote:

syzbot suspects this issue was fixed by commit:

commit 43016d02cf6e46edfc4696452251d34bba0c0435
Author: Florian Westphal [off-list ref]
Date:   Mon May 3 11:51:15 2021 +0000

    netfilter: arptables: use pernet ops struct during unregister

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10acd273300000
start commit:   c98ff1d013d2 Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=1c70e618af4c2e92
dashboard link: https://syzkaller.appspot.com/bug?extid=d6218cb2fae0b2411e9d
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=145cb2b6d00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=157b72b1d00000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: netfilter: arptables: use pernet ops struct during unregister

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

I guess this is a wrong commit and it was fixed by something in io_uring.
Searching for refcount fixes I see
a298232ee6b9a1d5d732aa497ff8be0d45b5bd82 "io_uring: fix link timeout
refs".
Pavel, does it look right to you?

On 9/16/21 8:59 AM, Dmitry Vyukov wrote:

On Mon, 13 Sept 2021 at 11:22, syzbot
[off-list ref] wrote:

quoted

syzbot suspects this issue was fixed by commit:

commit 43016d02cf6e46edfc4696452251d34bba0c0435
Author: Florian Westphal [off-list ref]
Date:   Mon May 3 11:51:15 2021 +0000

    netfilter: arptables: use pernet ops struct during unregister

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10acd273300000
start commit:   c98ff1d013d2 Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree:       upstream
kernel config:  https://syzkaller.appspot.com/x/.config?x=1c70e618af4c2e92
dashboard link: https://syzkaller.appspot.com/bug?extid=d6218cb2fae0b2411e9d
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=145cb2b6d00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=157b72b1d00000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: netfilter: arptables: use pernet ops struct during unregister

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

I guess this is a wrong commit and it was fixed by something in io_uring.
Searching for refcount fixes I see
a298232ee6b9a1d5d732aa497ff8be0d45b5bd82 "io_uring: fix link timeout
refs".
Pavel, does it look right to you?

I don't remember to be honest, if the dates fit, it can pretty well be it.
Let's test one thing to be sure it hasn't been shut just by coincidence.

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


-- 
Pavel Begunkov

Hello,

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

Reported-and-tested-by: syzbot+d6218cb2fae0b2411e9d@syzkaller.appspotmail.com

Tested on:

commit:         5318e5b9 io_uring: quiesce files reg
git tree:       https://github.com/isilence/linux.git syz_test_quiesce_files
kernel config:  https://syzkaller.appspot.com/x/.config?x=f7d9f99709463d21
dashboard link: https://syzkaller.appspot.com/bug?extid=d6218cb2fae0b2411e9d
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.

On Thu, 16 Sept 2021 at 16:01, syzbot
[off-list ref] wrote:

Hello,

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

Reported-and-tested-by: syzbot+d6218cb2fae0b2411e9d@syzkaller.appspotmail.com

Tested on:

commit:         5318e5b9 io_uring: quiesce files reg
git tree:       https://github.com/isilence/linux.git syz_test_quiesce_files
kernel config:  https://syzkaller.appspot.com/x/.config?x=f7d9f99709463d21
dashboard link: https://syzkaller.appspot.com/bug?extid=d6218cb2fae0b2411e9d
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.

OK, since it's not failing, I assume we can say:

#syz fix: io_uring: fix link timeout refs

(and it's better to close it with a wrong fix, then to keep it open
forever anyway)