syzbot


KASAN: null-ptr-deref Write in f2fs_issue_flush

Status: upstream: reported C repro on 2025/09/30 19:35
Bug presence: origin:lts
[Documentation on labels]
Reported-by: syzbot+3675940c01f6ac7388f3@syzkaller.appspotmail.com
First crash: 123d, last: 3d02h
Fix bisection: failed (error log)
  
Bug presence (2)
Date Name Commit Repro Result
2025/10/03 lts (merge base) 43bb85222e53 C [report] KASAN: null-ptr-deref Write in f2fs_issue_flush
2025/10/03 upstream (ToT) e406d57be7bd C Didn't crash
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 KASAN: null-ptr-deref Write in f2fs_issue_flush 12 C 5 7d08h 84d 0/2 upstream: reported C repro on 2025/11/09 06:59
linux-6.1 KASAN: null-ptr-deref Write in f2fs_issue_flush origin:lts-only 12 C error 3 19d 123d 0/3 upstream: reported C repro on 2025/10/01 01:02
Last patch testing requests (4)
Created Duration User Patch Repo Result
2026/01/27 22:16 8m retest repro android13-5.15-lts report log
2025/12/24 18:22 6m retest repro android13-5.15-lts report log
2025/10/15 09:00 16m retest repro android13-5.15-lts report log
2025/10/15 09:00 15m retest repro android13-5.15-lts report log

Sample crash report:
=======================================================
WARNING: The mand mount option has been deprecated and
         and is ignored by this kernel. Remove the mand
         option from the mount to silence this warning.
=======================================================
F2FS-fs (loop2): Try to recover all the superblocks, ret: 0
==================================================================
BUG: KASAN: null-ptr-deref in f2fs_issue_flush+0x161/0x8b0 fs/f2fs/segment.c:-1
Write of size 4 at addr 0000000000000024 by task syz.2.17/371

CPU: 0 PID: 371 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 __kasan_report mm/kasan/report.c:431 [inline]
 kasan_report+0xe7/0x140 mm/kasan/report.c:444
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x249/0x2a0 mm/kasan/generic.c:189
 __kasan_check_write+0x14/0x20 mm/kasan/shadow.c:37
 f2fs_issue_flush+0x161/0x8b0 fs/f2fs/segment.c:-1
 f2fs_do_sync_file+0x11aa/0x1bb0 fs/f2fs/file.c:381
 f2fs_sync_file+0x103/0x150 fs/f2fs/file.c:397
 vfs_fsync_range fs/sync.c:188 [inline]
 vfs_fsync+0x18d/0x1a0 fs/sync.c:202
 __loop_update_dio+0x259/0x600 drivers/block/loop.c:256
 loop_update_dio drivers/block/loop.c:675 [inline]
 loop_configure+0x107e/0x1710 drivers/block/loop.c:1307
 lo_ioctl+0xb88/0x2370 drivers/block/loop.c:1864
 blkdev_ioctl+0x304/0x680 block/ioctl.c:604
 block_ioctl+0xaf/0x100 block/fops.c:496
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:860
 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:860
 x64_sys_call+0x2f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f9ad1535eb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff20acf178 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9ad17b0fa0 RCX: 00007f9ad1535eb9
RDX: 00002000000002c0 RSI: 0000000000004c0a RDI: 0000000000000003
RBP: 00007f9ad15a3c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9ad17b0fac R14: 00007f9ad17b0fa0 R15: 00007f9ad17b0fa0
 </TASK>
==================================================================
BUG: kernel NULL pointer dereference, address: 0000000000000024
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 12d839067 P4D 12d839067 PUD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 371 Comm: syz.2.17 Tainted: G    B             syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:arch_atomic_inc fs/f2fs/segment.c:-1 [inline]
RIP: 0010:atomic_inc include/linux/atomic/atomic-instrumented.h:182 [inline]
RIP: 0010:f2fs_issue_flush+0x172/0x8b0 fs/f2fs/segment.c:595
Code: 03 52 ff 4c 89 64 24 28 49 83 c4 24 4c 89 e7 be 04 00 00 00 e8 7f 2c 91 ff 81 e3 00 04 00 00 0f 85 52 01 00 00 4c 89 64 24 08 <f0> 41 ff 04 24 4c 8b 74 24 20 4d 8d ae 3c 0c 00 00 4d 89 ec 49 c1
RSP: 0018:ffffc90000c36ec0 EFLAGS: 00010246
RAX: ffff888111339300 RBX: 0000000000000000 RCX: ffff8881113393c0
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00000000ffffffff
RBP: ffffc90000c36fd0 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff0e18a4c R12: 0000000000000024
R13: ffffc90000c36f20 R14: 0000000000000000 R15: 1ffff92000186de0
FS:  0000555579413500(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000024 CR3: 000000012d422000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 f2fs_do_sync_file+0x11aa/0x1bb0 fs/f2fs/file.c:381
 f2fs_sync_file+0x103/0x150 fs/f2fs/file.c:397
 vfs_fsync_range fs/sync.c:188 [inline]
 vfs_fsync+0x18d/0x1a0 fs/sync.c:202
 __loop_update_dio+0x259/0x600 drivers/block/loop.c:256
 loop_update_dio drivers/block/loop.c:675 [inline]
 loop_configure+0x107e/0x1710 drivers/block/loop.c:1307
 lo_ioctl+0xb88/0x2370 drivers/block/loop.c:1864
 blkdev_ioctl+0x304/0x680 block/ioctl.c:604
 block_ioctl+0xaf/0x100 block/fops.c:496
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:860
 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:860
 x64_sys_call+0x2f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f9ad1535eb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff20acf178 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9ad17b0fa0 RCX: 00007f9ad1535eb9
RDX: 00002000000002c0 RSI: 0000000000004c0a RDI: 0000000000000003
RBP: 00007f9ad15a3c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9ad17b0fac R14: 00007f9ad17b0fa0 R15: 00007f9ad17b0fa0
 </TASK>
Modules linked in:
CR2: 0000000000000024
---[ end trace 1c262f8b412defe5 ]---
RIP: 0010:arch_atomic_inc fs/f2fs/segment.c:-1 [inline]
RIP: 0010:atomic_inc include/linux/atomic/atomic-instrumented.h:182 [inline]
RIP: 0010:f2fs_issue_flush+0x172/0x8b0 fs/f2fs/segment.c:595
Code: 03 52 ff 4c 89 64 24 28 49 83 c4 24 4c 89 e7 be 04 00 00 00 e8 7f 2c 91 ff 81 e3 00 04 00 00 0f 85 52 01 00 00 4c 89 64 24 08 <f0> 41 ff 04 24 4c 8b 74 24 20 4d 8d ae 3c 0c 00 00 4d 89 ec 49 c1
RSP: 0018:ffffc90000c36ec0 EFLAGS: 00010246
RAX: ffff888111339300 RBX: 0000000000000000 RCX: ffff8881113393c0
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00000000ffffffff
RBP: ffffc90000c36fd0 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff0e18a4c R12: 0000000000000024
R13: ffffc90000c36f20 R14: 0000000000000000 R15: 1ffff92000186de0
FS:  0000555579413500(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000024 CR3: 000000012d422000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	03 52 ff             	add    -0x1(%rdx),%edx
   3:	4c 89 64 24 28       	mov    %r12,0x28(%rsp)
   8:	49 83 c4 24          	add    $0x24,%r12
   c:	4c 89 e7             	mov    %r12,%rdi
   f:	be 04 00 00 00       	mov    $0x4,%esi
  14:	e8 7f 2c 91 ff       	call   0xff912c98
  19:	81 e3 00 04 00 00    	and    $0x400,%ebx
  1f:	0f 85 52 01 00 00    	jne    0x177
  25:	4c 89 64 24 08       	mov    %r12,0x8(%rsp)
* 2a:	f0 41 ff 04 24       	lock incl (%r12) <-- trapping instruction
  2f:	4c 8b 74 24 20       	mov    0x20(%rsp),%r14
  34:	4d 8d ae 3c 0c 00 00 	lea    0xc3c(%r14),%r13
  3b:	4d 89 ec             	mov    %r13,%r12
  3e:	49                   	rex.WB
  3f:	c1                   	.byte 0xc1

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/29 10:07 android13-5.15-lts 7e1070528954 0adc945e .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 KASAN: null-ptr-deref Write in f2fs_issue_flush
2025/09/30 19:40 android13-5.15-lts 2bbc293701f8 65a0eece .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 KASAN: null-ptr-deref Write in f2fs_issue_flush
2025/09/30 19:24 android13-5.15-lts 2bbc293701f8 65a0eece .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 KASAN: null-ptr-deref Write in f2fs_issue_flush
2026/01/29 09:36 android13-5.15-lts 7e1070528954 0adc945e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: null-ptr-deref Write in f2fs_issue_flush
2025/09/30 17:50 android13-5.15-lts 2bbc293701f8 65a0eece .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: null-ptr-deref Write in f2fs_issue_flush
2025/09/30 17:50 android13-5.15-lts 2bbc293701f8 65a0eece .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: null-ptr-deref Write in f2fs_issue_flush
* Struck through repros no longer work on HEAD.