[kernel?] KASAN: null-ptr-deref Read in filemap_fault

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4b0f4525dc4f Add linux-next specific files for 20230331
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13d94d2ec80000
kernel config: https://syzkaller.appspot.com/x/.config?x=85cc4b935a1f7194
dashboard link: https://syzkaller.appspot.com/bug?extid=9303485bf1fc09813435
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
CC: [b...@vger.kernel.org da...@davemloft.net edum...@google.com ku...@kernel.org linux-...@vger.kernel.org net...@vger.kernel.org pab...@redhat.com richard...@gmail.com]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8d06bb015df3/disk-4b0f4525.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6a1c1ebf3724/vmlinux-4b0f4525.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4bb2b8d6cd7d/bzImage-4b0f4525.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+930348...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:68 [inline]
BUG: KASAN: null-ptr-deref in atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
BUG: KASAN: null-ptr-deref in page_ref_count include/linux/page_ref.h:67 [inline]
BUG: KASAN: null-ptr-deref in put_page_testzero include/linux/mm.h:1033 [inline]
BUG: KASAN: null-ptr-deref in folio_put_testzero include/linux/mm.h:1039 [inline]
BUG: KASAN: null-ptr-deref in folio_put include/linux/mm.h:1466 [inline]
BUG: KASAN: null-ptr-deref in filemap_fault+0x544/0x24a0 mm/filemap.c:3380
Read of size 4 at addr 0000000000000032 by task syz-executor.1/15650

CPU: 0 PID: 15650 Comm: syz-executor.1 Not tainted 6.3.0-rc4-next-20230331-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
print_report mm/kasan/report.c:465 [inline]
kasan_report+0xec/0x130 mm/kasan/report.c:572
check_region_inline mm/kasan/generic.c:181 [inline]
kasan_check_range+0x141/0x190 mm/kasan/generic.c:187
instrument_atomic_read include/linux/instrumented.h:68 [inline]
atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
page_ref_count include/linux/page_ref.h:67 [inline]
put_page_testzero include/linux/mm.h:1033 [inline]
folio_put_testzero include/linux/mm.h:1039 [inline]
folio_put include/linux/mm.h:1466 [inline]
filemap_fault+0x544/0x24a0 mm/filemap.c:3380
__do_fault+0x107/0x600 mm/memory.c:4177
do_read_fault mm/memory.c:4531 [inline]
do_fault mm/memory.c:4660 [inline]
do_pte_missing mm/memory.c:3648 [inline]
handle_pte_fault mm/memory.c:4948 [inline]
__handle_mm_fault+0x2806/0x4180 mm/memory.c:5090
handle_mm_fault+0x2c0/0x9c0 mm/memory.c:5236
do_user_addr_fault+0x53d/0x1240 arch/x86/mm/fault.c:1462
handle_page_fault arch/x86/mm/fault.c:1556 [inline]
exc_page_fault+0x98/0x170 arch/x86/mm/fault.c:1612
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
RIP: 0010:copy_user_short_string+0xa/0x40 arch/x86/lib/copy_user_64.S:232
Code: 83 f8 12 74 0a 89 d1 f3 a4 89 c8 0f 01 ca c3 89 d0 0f 01 ca c3 01 ca eb e7 0f 1f 80 00 00 00 00 89 d1 83 e2 07 c1 e9 03 74 12 <4c> 8b 06 4c 89 07 48 8d 76 08 48 8d 7f 08 ff c9 75 ee 21 d2 74 10
RSP: 0018:ffffc900059dfa00 EFLAGS: 00050202
RAX: 0000000000000001 RBX: 0000000000000038 RCX: 0000000000000007
RDX: 0000000000000000 RSI: 000000002000a000 RDI: ffffc900059dfa50
RBP: ffffc900059dfa50 R08: 0000000000000001 R09: ffffc900059dfa87
R10: fffff52000b3bf50 R11: 0000000000000000 R12: 00007fffffffefc8
R13: 000000002000a000 R14: 0000000000000000 R15: ffffc900059dfb38
copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
raw_copy_from_user arch/x86/include/asm/uaccess_64.h:52 [inline]
_copy_from_user+0x147/0x180 lib/usercopy.c:23
copy_from_user include/linux/uaccess.h:183 [inline]
copy_msghdr_from_user+0x89/0x150 net/socket.c:2432
sendmsg_copy_msghdr net/socket.c:2532 [inline]
___sys_sendmsg+0xdd/0x1b0 net/socket.c:2551
__sys_sendmmsg+0x18f/0x460 net/socket.c:2641
__do_sys_sendmmsg net/socket.c:2670 [inline]
__se_sys_sendmmsg net/socket.c:2667 [inline]
__x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2667
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f388248c0f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f3883160168 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f38825ac120 RCX: 00007f388248c0f9
RDX: 040000000000035c RSI: 0000000020001700 RDI: 0000000000000009
RBP: 00007f38824e7b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffeb479d36f R14: 00007f3883160300 R15: 0000000000022000
</TASK>
==================================================================
----------------
Code disassembly (best guess):
0: 83 f8 12 cmp $0x12,%eax
3: 74 0a je 0xf
5: 89 d1 mov %edx,%ecx
7: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi)
9: 89 c8 mov %ecx,%eax
b: 0f 01 ca clac
e: c3 retq
f: 89 d0 mov %edx,%eax
11: 0f 01 ca clac
14: c3 retq
15: 01 ca add %ecx,%edx
17: eb e7 jmp 0x0
19: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
20: 89 d1 mov %edx,%ecx
22: 83 e2 07 and $0x7,%edx
25: c1 e9 03 shr $0x3,%ecx
28: 74 12 je 0x3c
* 2a: 4c 8b 06 mov (%rsi),%r8 <-- trapping instruction
2d: 4c 89 07 mov %r8,(%rdi)
30: 48 8d 76 08 lea 0x8(%rsi),%rsi
34: 48 8d 7f 08 lea 0x8(%rdi),%rdi
38: ff c9 dec %ecx
3a: 75 ee jne 0x2a
3c: 21 d2 and %edx,%edx
3e: 74 10 je 0x50


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