linux-kernel - Re: [syzbot] [block?] general protection fault in blk_mq_free_tags

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Message-ID: <CAFj5m9+H9t_ytndYk=iA1QvAXbgLFGXJ+5_CmSXpEpQDye-jyQ@mail.gmail.com>
Date: Tue, 23 Sep 2025 11:28:09 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Hillf Danton <hdanton@...a.com>
Cc: syzbot <syzbot+5c5d41e80248d610221f@...kaller.appspotmail.com>, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [block?] general protection fault in blk_mq_free_tags_callback

On Tue, Sep 23, 2025 at 6:59 AM Hillf Danton <hdanton@...a.com> wrote:
>
> > Date: Mon, 22 Sep 2025 13:24:25 -0700 [thread overview]
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    846bd2225ec3 Add linux-next specific files for 20250919
> > git tree:       linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=13c238e2580000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=135377594f35b576
> > dashboard link: https://syzkaller.appspot.com/bug?extid=5c5d41e80248d610221f
> > compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=155e427c580000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17bb8142580000
>
> #syz test linux-next  master
>
> --- x/block/blk-mq-tag.c
> +++ y/block/blk-mq-tag.c
> @@ -565,6 +565,7 @@ struct blk_mq_tags *blk_mq_init_tags(uns
>         if (!tags)
>                 return NULL;
>
> +       INIT_LIST_HEAD(&tags->page_list);
>         tags->nr_tags = total_tags;
>         tags->nr_reserved_tags = reserved_tags;
>         spin_lock_init(&tags->lock);

The initialization is needed, otherwise the unitialized tags->page_list
may be accessed in the error code path of blk_mq_alloc_rq_map().

Thanks,