KASAN: user-memory-access Read in put_page

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: bef7b2a7 Merge tag 'devicetree-for-5.7' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16940efbe00000
kernel config: https://syzkaller.appspot.com/x/.config?x=f72ba8a207627d60
dashboard link: https://syzkaller.appspot.com/bug?extid=b4501d3e966ff59f6090
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15d79efbe00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1705901be00000

The bug was bisected to:

commit 4426e945df588f2878affddf88a51259200f7e29
Author: Peter Xu <pet...@redhat.com>
Date: Thu Apr 2 04:08:49 2020 +0000

mm/gup: allow VM_FAULT_RETRY for multiple times

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1441b1fbe00000
final crash: https://syzkaller.appspot.com/x/report.txt?x=1641b1fbe00000
console output: https://syzkaller.appspot.com/x/log.txt?x=1241b1fbe00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+b4501d...@syzkaller.appspotmail.com
Fixes: 4426e945df58 ("mm/gup: allow VM_FAULT_RETRY for multiple times")

==================================================================
BUG: KASAN: user-memory-access in atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
BUG: KASAN: user-memory-access in page_ref_count include/linux/page_ref.h:67 [inline]
BUG: KASAN: user-memory-access in put_page_testzero include/linux/mm.h:675 [inline]
BUG: KASAN: user-memory-access in put_page+0x110/0x1d0 include/linux/mm.h:1136
Read of size 4 at addr 00003fbf7e8680b0 by task syz-executor574/7201

CPU: 0 PID: 7201 Comm: syz-executor574 Not tainted 5.6.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1e9/0x30e lib/dump_stack.c:118
__kasan_report+0x122/0x190 mm/kasan/report.c:507
kasan_report+0x4d/0x80 mm/kasan/common.c:648
==================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 7201 Comm: syz-executor574 Tainted: G B 5.6.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1e9/0x30e lib/dump_stack.c:118
panic+0x264/0x7a0 kernel/panic.c:221
end_report mm/kasan/report.c:96 [inline]
__kasan_report+0x187/0x190 mm/kasan/report.c:510
kasan_report+0x4d/0x80 mm/kasan/common.c:648
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
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[Andrew Morton]

On Mon, 06 Apr 2020 11:16:13 -0700 syzbot <syzbot+b4501d...@syzkaller.appspotmail.com> wrote:

> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: bef7b2a7 Merge tag 'devicetree-for-5.7' of git://git.kerne..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16940efbe00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=f72ba8a207627d60
> dashboard link: https://syzkaller.appspot.com/bug?extid=b4501d3e966ff59f6090
> compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15d79efbe00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1705901be00000
>
> The bug was bisected to:
>
> commit 4426e945df588f2878affddf88a51259200f7e29
> Author: Peter Xu <pet...@redhat.com>
> Date: Thu Apr 2 04:08:49 2020 +0000
>
> mm/gup: allow VM_FAULT_RETRY for multiple times
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1441b1fbe00000
> final crash: https://syzkaller.appspot.com/x/report.txt?x=1641b1fbe00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=1241b1fbe00000

Thanks. This looks like a duplicate of your report
syzbot+693dc1...@syzkaller.appspotmail.com ("BUG: unable to
handle kernel paging request in kernel_get_mempolicy").

The bisection is believable but I can't spot why 4426e945df58 would
have messed up get_user_pages_locked() in this fashion - I've asked
Peter to take a look.

[Eric Biggers]

#syz dup: BUG: unable to handle kernel paging request in kernel_get_mempolicy