Re: [syzbot] general protection fault in set_task_ioprio

5 messages, 3 authors, 2021-12-21 · open the first message on its own page

Re: [syzbot] general protection fault in set_task_ioprio

From: syzbot <hidden>
Date: 2021-12-21 09:52:11 

syzbot has bisected this issue to:

commit e4b8954074f6d0db01c8c97d338a67f9389c042f
Author: Eric Dumazet [off-list ref]
Date:   Tue Dec 7 01:30:37 2021 +0000

    netlink: add net device refcount tracker to struct ethnl_req_info

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10620fcdb00000
start commit:   07f8c60fe60f Add linux-next specific files for 20211220
git tree:       linux-next
final oops:     https://syzkaller.appspot.com/x/report.txt?x=12620fcdb00000
console output: https://syzkaller.appspot.com/x/log.txt?x=14620fcdb00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2060504830b9124a
dashboard link: https://syzkaller.appspot.com/bug?extid=8836466a79f4175961b0
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12058fcbb00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17141adbb00000

Reported-by: syzbot+8836466a79f4175961b0@syzkaller.appspotmail.com
Fixes: e4b8954074f6 ("netlink: add net device refcount tracker to struct ethnl_req_info")

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

Re: [syzbot] general protection fault in set_task_ioprio

From: Eric Dumazet <hidden>
Date: 2021-12-21 10:44:51 

On Tue, Dec 21, 2021 at 1:52 AM syzbot
[off-list ref] wrote:
syzbot has bisected this issue to:

commit e4b8954074f6d0db01c8c97d338a67f9389c042f
Author: Eric Dumazet [off-list ref]
Date:   Tue Dec 7 01:30:37 2021 +0000

    netlink: add net device refcount tracker to struct ethnl_req_info
Unfortunately this commit will be in the way of many bisections.

Real bug was added in

commit 5fc11eebb4a98df5324a4de369bb5ab7f0007ff7
Author: Christoph Hellwig [off-list ref]
Date:   Thu Dec 9 07:31:29 2021 +0100

    block: open code create_task_io_context in set_task_ioprio

    The flow in set_task_ioprio can be simplified by simply open coding
    create_task_io_context, which removes a refcount roundtrip on the I/O
    context.

    Signed-off-by: Christoph Hellwig [off-list ref]
    Reviewed-by: Jan Kara [off-list ref]
    Link: https://lore.kernel.org/r/20211209063131.18537-10-hch@lst.de
    Signed-off-by: Jens Axboe [off-list ref]


bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10620fcdb00000
start commit:   07f8c60fe60f Add linux-next specific files for 20211220
git tree:       linux-next
final oops:     https://syzkaller.appspot.com/x/report.txt?x=12620fcdb00000
console output: https://syzkaller.appspot.com/x/log.txt?x=14620fcdb00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2060504830b9124a
dashboard link: https://syzkaller.appspot.com/bug?extid=8836466a79f4175961b0
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12058fcbb00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17141adbb00000

Reported-by: syzbot+8836466a79f4175961b0@syzkaller.appspotmail.com
Fixes: e4b8954074f6 ("netlink: add net device refcount tracker to struct ethnl_req_info")

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

Re: [syzbot] general protection fault in set_task_ioprio

From: Jens Axboe <axboe@kernel.dk>
Date: 2021-12-21 15:25:10 

On 12/21/21 3:44 AM, Eric Dumazet wrote:
On Tue, Dec 21, 2021 at 1:52 AM syzbot
[off-list ref] wrote:
quoted
syzbot has bisected this issue to:

commit e4b8954074f6d0db01c8c97d338a67f9389c042f
Author: Eric Dumazet [off-list ref]
Date:   Tue Dec 7 01:30:37 2021 +0000

    netlink: add net device refcount tracker to struct ethnl_req_info
Unfortunately this commit will be in the way of many bisections.

Real bug was added in

commit 5fc11eebb4a98df5324a4de369bb5ab7f0007ff7
Author: Christoph Hellwig [off-list ref]
Date:   Thu Dec 9 07:31:29 2021 +0100

    block: open code create_task_io_context in set_task_ioprio

    The flow in set_task_ioprio can be simplified by simply open coding
    create_task_io_context, which removes a refcount roundtrip on the I/O
    context.

    Signed-off-by: Christoph Hellwig [off-list ref]
    Reviewed-by: Jan Kara [off-list ref]
    Link: https://lore.kernel.org/r/20211209063131.18537-10-hch@lst.de
    Signed-off-by: Jens Axboe [off-list ref]
There are only really 5 patches in between the broken commit and the one
that fixes it, and it only affects things trying to set the ioprio with
a dead task. Is this a huge issue? I don't see why this would cause a
lot of bisection headaches.

-- 
Jens Axboe

Re: [syzbot] general protection fault in set_task_ioprio

From: Eric Dumazet <hidden>
Date: 2021-12-21 16:04:12 

On Tue, Dec 21, 2021 at 7:25 AM Jens Axboe [off-list ref] wrote:
On 12/21/21 3:44 AM, Eric Dumazet wrote:
quoted
On Tue, Dec 21, 2021 at 1:52 AM syzbot
[off-list ref] wrote:
quoted
syzbot has bisected this issue to:

commit e4b8954074f6d0db01c8c97d338a67f9389c042f
Author: Eric Dumazet [off-list ref]
Date:   Tue Dec 7 01:30:37 2021 +0000

    netlink: add net device refcount tracker to struct ethnl_req_info
Unfortunately this commit will be in the way of many bisections.

Real bug was added in

commit 5fc11eebb4a98df5324a4de369bb5ab7f0007ff7
Author: Christoph Hellwig [off-list ref]
Date:   Thu Dec 9 07:31:29 2021 +0100

    block: open code create_task_io_context in set_task_ioprio

    The flow in set_task_ioprio can be simplified by simply open coding
    create_task_io_context, which removes a refcount roundtrip on the I/O
    context.

    Signed-off-by: Christoph Hellwig [off-list ref]
    Reviewed-by: Jan Kara [off-list ref]
    Link: https://lore.kernel.org/r/20211209063131.18537-10-hch@lst.de
    Signed-off-by: Jens Axboe [off-list ref]
There are only really 5 patches in between the broken commit and the one
that fixes it, and it only affects things trying to set the ioprio with
a dead task. Is this a huge issue? I don't see why this would cause a
lot of bisection headaches.
I was saying that my commit was polluting syzbot bisection, this is a
distraction in this report.
(Or if you prefer, please ignore syzbot bisection)

linux-next has still this bug in set_task_ioprio()


--
Jens Axboe

Re: [syzbot] general protection fault in set_task_ioprio

From: Jens Axboe <axboe@kernel.dk>
Date: 2021-12-21 16:30:11 

On 12/21/21 9:03 AM, Eric Dumazet wrote:
On Tue, Dec 21, 2021 at 7:25 AM Jens Axboe [off-list ref] wrote:
quoted
On 12/21/21 3:44 AM, Eric Dumazet wrote:
quoted
On Tue, Dec 21, 2021 at 1:52 AM syzbot
[off-list ref] wrote:
quoted
syzbot has bisected this issue to:

commit e4b8954074f6d0db01c8c97d338a67f9389c042f
Author: Eric Dumazet [off-list ref]
Date:   Tue Dec 7 01:30:37 2021 +0000

    netlink: add net device refcount tracker to struct ethnl_req_info
Unfortunately this commit will be in the way of many bisections.

Real bug was added in

commit 5fc11eebb4a98df5324a4de369bb5ab7f0007ff7
Author: Christoph Hellwig [off-list ref]
Date:   Thu Dec 9 07:31:29 2021 +0100

    block: open code create_task_io_context in set_task_ioprio

    The flow in set_task_ioprio can be simplified by simply open coding
    create_task_io_context, which removes a refcount roundtrip on the I/O
    context.

    Signed-off-by: Christoph Hellwig [off-list ref]
    Reviewed-by: Jan Kara [off-list ref]
    Link: https://lore.kernel.org/r/20211209063131.18537-10-hch@lst.de
    Signed-off-by: Jens Axboe [off-list ref]
There are only really 5 patches in between the broken commit and the one
that fixes it, and it only affects things trying to set the ioprio with
a dead task. Is this a huge issue? I don't see why this would cause a
lot of bisection headaches.
I was saying that my commit was polluting syzbot bisection, this is a
distraction in this report.
(Or if you prefer, please ignore syzbot bisection)
Ah got it, yes makes sense.

linux-next has still this bug in set_task_ioprio()
linux-next often trails by a few days, once it catches up hopefully
this will be behind us.

-- 
Jens Axboe
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