From: syzbot <syzbot+c87be4f669d920c76330@syzkaller.appspotmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: akpm@linux-foundation.org, bp@alien8.de, frederic@kernel.org,
hpa@zytor.com, jmattson@google.com, joro@8bytes.org,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, mark.rutland@arm.com, masahiroy@kernel.org,
mingo@redhat.com, npiggin@gmail.com, pbonzini@redhat.com,
peterz@infradead.org, rafael.j.wysocki@intel.com,
rostedt@goodmis.org, seanjc@google.com, sedat.dilek@gmail.com,
syzkaller-bugs@googlegroups.com, tglx@linutronix.de,
vitor@massaru.org, vkuznets@redhat.com, wanpengli@tencent.com,
will@kernel.org, willy@infradead.org, x86@kernel.org
Subject: Re: [syzbot] kernel BUG in find_lock_entries
Date: Mon, 09 Aug 2021 15:54:40 -0700 [thread overview]
Message-ID: <00000000000033f7f705c9284592@google.com> (raw)
In-Reply-To: <YRGxNaVc1cGsyd0Y@casper.infradead.org>
> On Mon, Aug 09, 2021 at 02:02:22PM -0700, syzbot wrote:
>> The issue was bisected to:
>>
>> commit 997acaf6b4b59c6a9c259740312a69ea549cc684
>> Author: Mark Rutland <mark.rutland@arm.com>
>> Date: Mon Jan 11 15:37:07 2021 +0000
>>
>> lockdep: report broken irq restoration
>
> That's just a bogus bisection. The correct bad commit is 5c211ba29deb.
>
>> kernel BUG at mm/filemap.c:2041!
>> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
>> CPU: 1 PID: 24786 Comm: syz-executor626 Not tainted 5.14.0-rc4-syzkaller #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>> RIP: 0010:find_lock_entries+0x10d5/0x1110 mm/filemap.c:2041
>
> This patch should fix it. It's not just removing the warning; this
> warning duplicates the warning a few lines down (after taking the
> lock). It's not safe to make this assertion without holding the page
> lock as the page can move between the page cache and the swap cache.
>
> #syz test
want 2 args (repo, branch), got 4
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index d1458ecf2f51..34de0b14aaa9 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2038,7 +2038,6 @@ unsigned find_lock_entries(struct address_space *mapping, pgoff_t start,
> if (!xa_is_value(page)) {
> if (page->index < start)
> goto put;
> - VM_BUG_ON_PAGE(page->index != xas.xa_index, page);
> if (page->index + thp_nr_pages(page) - 1 > end)
> goto put;
> if (!trylock_page(page))
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/YRGxNaVc1cGsyd0Y%40casper.infradead.org.
prev parent reply other threads:[~2021-08-09 22:54 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-09 21:02 [syzbot] kernel BUG in find_lock_entries syzbot
2021-08-09 22:50 ` Matthew Wilcox
2021-08-09 22:51 ` syzbot
2021-08-09 22:54 ` syzbot [this message]
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