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From: Thomas Gleixner <tglx@kernel.org>
To: syzbot <syzbot+237b5b985b78c1da9600@syzkaller.appspotmail.com>,
	andrealmeid@igalia.com, dave@stgolabs.net, dvhart@infradead.org,
	linux-kernel@vger.kernel.org, mingo@redhat.com,
	peterz@infradead.org, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [kernel?] WARNING in __mmdrop (2)
Date: Tue, 10 Feb 2026 20:00:30 +0100	[thread overview]
Message-ID: <87o6lwa0fl.ffs@tglx> (raw)
In-Reply-To: <698aaf3c.050a0220.3b3015.0088.GAE@google.com>

On Mon, Feb 09 2026 at 20:08, syzbot wrote:
> HEAD commit:    05f7e89ab973 Linux 6.19
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1153465a580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=df890e720d1bb80
> dashboard link: https://syzkaller.appspot.com/bug?extid=237b5b985b78c1da9600
> compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=105297fa580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=120c12e6580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/ea9f39c5175d/disk-05f7e89a.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/734edeebfa32/vmlinux-05f7e89a.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/a2cb36d849f0/bzImage-05f7e89a.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+237b5b985b78c1da9600@syzkaller.appspotmail.com

Futexes are just a red herring here. The bug is a double mmput()
introduced by:

  b5cbacd7f86f ("procfs: avoid fetching build ID while holding VMA lock")

See
        https://lore.kernel.org/all/87qzqsa1br.ffs@tglx/

Thanks,

        tglx

      reply	other threads:[~2026-02-10 19:00 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-02-10  4:08 [syzbot] [kernel?] WARNING in __mmdrop (2) syzbot
2026-02-10 19:00 ` Thomas Gleixner [this message]

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