Subject: [syzbot] [mm?] [net?] KASAN: null-ptr-deref Read in filemap_fault

From: syzbot <[email-masked]>
Date: Fri, 28 Apr 2023 06:25:53 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    33afd4b76393 Merge tag 'mm-nonmm-stable-2023-04-27-16-01' ..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17bc1008280000
kernel config:  https://syzkaller.appspot.com/x/.config?x=70288413d8a92398
dashboard link: https://syzkaller.appspot.com/bug?extid=48011b86c8ea329af1b9
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: i386

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
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:1007 [inline]
BUG: KASAN: null-ptr-deref in folio_put_testzero include/linux/mm.h:1013 [inline]
BUG: KASAN: null-ptr-deref in folio_put include/linux/mm.h:1440 [inline]
BUG: KASAN: null-ptr-deref in filemap_fault+0x544/0x24a0 mm/filemap.c:3382
Read of size 4 at addr 0000000000000028 by task syz-executor.2/19418

CPU: 1 PID: 19418 Comm: syz-executor.2 Not tainted 6.3.0-syzkaller-10620-g33afd4b76393 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
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:1007 [inline]
 folio_put_testzero include/linux/mm.h:1013 [inline]
 folio_put include/linux/mm.h:1440 [inline]
 filemap_fault+0x544/0x24a0 mm/filemap.c:3382
 __do_fault+0x107/0x600 mm/memory.c:4176
 do_read_fault mm/memory.c:4530 [inline]
 do_fault mm/memory.c:4659 [inline]
 do_pte_missing mm/memory.c:3647 [inline]
 handle_pte_fault mm/memory.c:4947 [inline]
 __handle_mm_fault+0x27f6/0x4170 mm/memory.c:5089
 handle_mm_fault+0x2af/0x9f0 mm/memory.c:5243
 do_user_addr_fault+0x51a/0x1210 arch/x86/mm/fault.c:1440
 handle_page_fault arch/x86/mm/fault.c:1534 [inline]
 exc_page_fault+0x98/0x170 arch/x86/mm/fault.c:1590
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
RIP: 0023:0xf72255d0
Code: Unable to access opcode bytes at 0xf72255a6.
RSP: 002b:00000000ffb4674c EFLAGS: 00010202
RAX: 00000000f734e000 RBX: 00000000f734e000 RCX: 00000000f737c038
RDX: 000000002e220000 RSI: 0000000000000004 RDI: 00000000000e257f
RBP: 00000000f737c0c0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000282 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
==================================================================

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