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From:   Vishal Moola <vishal.moola@gmail.com>
Date:   Wed, 18 Oct 2023 14:30:59 -0700
Message-ID: <CAOzc2pxr_Lzgbv-ddvifVdcOrA0X-2Y8Zz+WHjFWAuGu_CdZnA@mail.gmail.com>
Subject: Re: [syzbot] [mm?] [fs?] general protection fault in folio_flags
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     syzbot <syzbot+1e2648076cadf48ad9a1@syzkaller.appspotmail.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, syzkaller-bugs@googlegroups.com
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On Wed, Oct 18, 2023 at 1:49=E2=80=AFPM Andrew Morton <akpm@linux-foundatio=
n.org> wrote:
>
> On Wed, 18 Oct 2023 12:29:47 -0700 syzbot <syzbot+1e2648076cadf48ad9a1@sy=
zkaller.appspotmail.com> wrote:
>
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    2dac75696c6d Add linux-next specific files for 20231018
> > git tree:       linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=3D13858275680=
000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=3D6f8545e1ef7=
a2b66
> > dashboard link: https://syzkaller.appspot.com/bug?extid=3D1e2648076cadf=
48ad9a1
> > 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=3D17543ee56=
80000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=3D101f5fe5680=
000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/2375f16ed327/d=
isk-2dac7569.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/c80aee6e2e6c/vmli=
nux-2dac7569.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/664dc23b738d=
/bzImage-2dac7569.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the co=
mmit:
> > Reported-by: syzbot+1e2648076cadf48ad9a1@syzkaller.appspotmail.com
>
> Thanks.
>
> > general protection fault, probably for non-canonical address 0xdffffc00=
00000000: 0000 [#1] PREEMPT SMP KASA
> > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> > CPU: 1 PID: 5710 Comm: syz-executor155 Not tainted 6.6.0-rc6-next-20231=
018-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS=
 Google 09/06/2023
> > RIP: 0010:PageTail include/linux/page-flags.h:286 [inline]
> > RIP: 0010:folio_flags.constprop.0+0x21/0x150 include/linux/page-flags.h=
:313
> > Code: 84 00 00 00 00 00 0f 1f 00 41 54 55 53 48 89 fb e8 14 2f a4 ff 48=
 8d 7b 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 =
0f 85 00 01 00 00 48 8b 6b 08 31 ff 83 e5 01 48 89 ee
> > RSP: 0018:ffffc90004367968 EFLAGS: 00010247
> > RAX: dffffc0000000000 RBX: fffffffffffffffe RCX: ffffffff81b7e126
> > RDX: 0000000000000000 RSI: ffffffff81e49d1c RDI: 0000000000000006
> > RBP: 0000000020200000 R08: 0000000000000005 R09: 0000000000000000
> > R10: 0000000000000000 R11: 1ffffffff1976fb9 R12: ffff88801675b900
> > R13: ffff888025f9f680 R14: fffffffffffffffe R15: 1ffff9200086cf3d
> > FS:  00007f2f2a17c6c0(0000) GS:ffff8880b9900000(0000) knlGS:00000000000=
00000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007f2f2a17cd58 CR3: 000000001bfa0000 CR4: 00000000003506f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >  <TASK>
> >  folio_test_head include/linux/page-flags.h:790 [inline]
> >  folio_test_large include/linux/page-flags.h:811 [inline]
> >  folio_order include/linux/mm.h:1079 [inline]
> >  collapse_pte_mapped_thp+0x42d/0x13b0 mm/khugepaged.c:1512
>
> Vishal, could you please take a look?

Yes of course. This looks to be caused by filemap_lock_folio()
returning an ERR_PTR() which wasn't an issue prior as
find_lock_page()/pagecache_get_page() was checking that
before returning a page.

#syz test: https://github.com/VMoola/kernel.git
34d60af8cb66d6f582c1aeade01689e94e8a0092


> >  madvise_collapse+0x875/0xaf0 mm/khugepaged.c:2761
> >  madvise_vma_behavior+0x1fe/0x1d00 mm/madvise.c:1086
> >  madvise_walk_vmas+0x1cf/0x2c0 mm/madvise.c:1260
> >  do_madvise+0x333/0x660 mm/madvise.c:1440
> >  __do_sys_madvise mm/madvise.c:1453 [inline]
> >  __se_sys_madvise mm/madvise.c:1451 [inline]
> >  __x64_sys_madvise+0xaa/0x110 mm/madvise.c:1451
> >  do_syscall_x64 arch/x86/entry/common.c:51 [inline]
> >  do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
> >  entry_SYSCALL_64_after_hwframe+0x63/0x6b
> > RIP: 0033:0x7f2f2a1dc7a9
> > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 01 1a 00 00 90 48 89 f8 48 89=
 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 =
ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
> > RSP: 002b:00007f2f2a17c238 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
> > RAX: ffffffffffffffda RBX: 00007f2f2a266318 RCX: 00007f2f2a1dc7a9
> > RDX: 0000000000000019 RSI: 000000000060005f RDI: 0000000020000000
> > RBP: 00007f2f2a266310 R08: 00007ffe616d77f7 R09: 00007f2f2a17c6c0
> > R10: 0000000000000000 R11: 0000000000000246 R12: b635773f07ebbeef
> > R13: 000000000000006e R14: 00007ffe616d7710 R15: 00007ffe616d77f8
> >
> > ...
> >