From: Suren Baghdasaryan <surenb@google.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: syzbot <syzbot+b591856e0f0139f83023@syzkaller.appspotmail.com>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [mm?] kernel BUG in vma_replace_policy
Date: Tue, 12 Sep 2023 08:03:08 -0700 [thread overview]
Message-ID: <CAJuCfpGEa504z1pgqR9KtCWQPESTcRcu8xoyxcNOv=6t4R+ong@mail.gmail.com> (raw)
In-Reply-To: <ZQB76G/6NxVgoE9u@casper.infradead.org>
On Tue, Sep 12, 2023 at 7:55 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Tue, Sep 12, 2023 at 06:30:46AM +0100, Matthew Wilcox wrote:
> > On Tue, Sep 05, 2023 at 06:03:49PM -0700, syzbot wrote:
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit: a47fc304d2b6 Add linux-next specific files for 20230831
> > > git tree: linux-next
> > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=16502ddba80000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=6ecd2a74f20953b9
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=b591856e0f0139f83023
> > > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=120e7d70680000
> > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1523f9c0680000
> > >
> > > Downloadable assets:
> > > disk image: https://storage.googleapis.com/syzbot-assets/b2e8f4217527/disk-a47fc304.raw.xz
> > > vmlinux: https://storage.googleapis.com/syzbot-assets/ed6cdcc09339/vmlinux-a47fc304.xz
> > > kernel image: https://storage.googleapis.com/syzbot-assets/bd9b2475bf5a/bzImage-a47fc304.xz
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+b591856e0f0139f83023@syzkaller.appspotmail.com
> >
> > #syz test
> >
> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > index 42b5567e3773..90ad5fe60824 100644
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -1342,6 +1342,7 @@ static long do_mbind(unsigned long start, unsigned long len,
> > vma_iter_init(&vmi, mm, start);
> > prev = vma_prev(&vmi);
> > for_each_vma_range(vmi, vma, end) {
> > + vma_start_write(vma);
> > err = mbind_range(&vmi, vma, &prev, start, end, new);
> > if (err)
> > break;
>
> Suren, can you take a look at this? The VMA should be locked by the
> call to queue_pages_range(), but by the time we get to here, the VMA
> isn't locked. I don't see anywhere that we cycle the mmap_lock (which
> would unlock the VMA), but I could have missed something. The two
> VMA walks should walk over the same set of VMAs. Certainly the VMA
> being dumped should have been locked by the pagewalk:
Sure, I'll look into this today. Somehow this report slipped by me
unnoticed. Thanks!
>
> vma ffff888077381a00 start 0000000020c2a000 end 0000000021000000 mm ffff8880258a8980
> prot 25 anon_vma 0000000000000000 vm_ops 0000000000000000
> pgoff 20c2a file 0000000000000000 private_data 0000000000000000
> flags: 0x8100077(read|write|exec|mayread|maywrite|mayexec|account|softdirty)
>
> syscall(__NR_mbind, /*addr=*/0x20400000ul, /*len=*/0xc00000ul, /*mode=*/4ul,
> /*nodemask=*/0ul, /*maxnode=*/0ul, /*flags=*/3ul);
>
> 20400000 + c00000 should overlap 20c2a000-21000000
next prev parent reply other threads:[~2023-09-12 15:03 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-06 1:03 [syzbot] [mm?] kernel BUG in vma_replace_policy syzbot
[not found] ` <20230906061902.591996-1-eadavis@sina.com>
2023-09-06 12:06 ` [PATCH] mm: as the same logic with queue_pages_range Matthew Wilcox
2023-09-12 5:20 ` kernel test robot
2023-09-13 9:10 ` [LTP] " Cyril Hrubis
2023-09-08 18:04 ` [syzbot] [mm?] kernel BUG in vma_replace_policy syzbot
2023-09-12 5:30 ` Matthew Wilcox
2023-09-12 6:09 ` syzbot
2023-09-12 14:55 ` Matthew Wilcox
2023-09-12 15:03 ` Suren Baghdasaryan [this message]
2023-09-12 16:00 ` Suren Baghdasaryan
2023-09-13 16:05 ` Suren Baghdasaryan
2023-09-13 16:46 ` Suren Baghdasaryan
2023-09-14 18:20 ` Suren Baghdasaryan
2023-09-14 19:09 ` Matthew Wilcox
2023-09-14 20:00 ` Suren Baghdasaryan
2023-09-14 20:53 ` Suren Baghdasaryan
2023-09-14 21:24 ` Matthew Wilcox
2023-09-14 22:21 ` Suren Baghdasaryan
2023-09-15 4:26 ` Hugh Dickins
2023-09-15 16:09 ` Suren Baghdasaryan
2023-09-15 18:05 ` Suren Baghdasaryan
2023-09-16 2:43 ` Hugh Dickins
2023-09-18 21:20 ` Suren Baghdasaryan
2023-09-15 18:26 ` Matthew Wilcox
2023-09-16 2:54 ` Hugh Dickins
2023-09-16 1:35 ` Yang Shi
2023-09-16 3:57 ` Hugh Dickins
2023-09-18 22:34 ` Yang Shi
2023-09-19 0:34 ` Hugh Dickins
[not found] <20230909034207.5816-1-hdanton@sina.com>
2023-09-09 4:43 ` syzbot
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