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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: 274d, last: 4d10h
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 9 7d10h 235d 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 170d 274d 0/3 upstream: reported C repro on 2025/10/01 01:02
▶ ▼ Last patch testing requests (7)
Created Duration User Patch Repo Result
2026/06/21 18:45 16m retest repro android13-5.15-lts log
2026/05/14 10:02 15m retest repro android13-5.15-lts report log
2026/04/27 23:51 39m retest repro android13-5.15-lts report log
2026/04/08 01:13 17m retest repro android13-5.15-lts report log
2026/03/04 19:09 6m retest repro android13-5.15-lts report log
2026/02/12 10:09 8m retest repro android13-5.15-lts report log
2026/02/12 10:08 6m retest repro android13-5.15-lts report log

Sample crash report:
==================================================================
BUG: KASAN: null-ptr-deref in f2fs_issue_flush+0x157/0x8b0 fs/f2fs/segment.c:-1
Write of size 4 at addr 0000000000000024 by task syz.2.17/372

CPU: 0 PID: 372 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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+0xcc/0x150 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+0x157/0x8b0 fs/f2fs/segment.c:-1
 f2fs_do_sync_file+0x11ae/0x1b70 fs/f2fs/file.c:384
 f2fs_sync_file+0x103/0x150 fs/f2fs/file.c:400
 vfs_fsync_range+0x171/0x180 fs/sync.c:188
 generic_write_sync include/linux/fs.h:3038 [inline]
 f2fs_file_write_iter+0x60d/0x29f0 fs/f2fs/file.c:4826
 call_write_iter include/linux/fs.h:2212 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x831/0xfd0 fs/read_write.c:594
 ksys_write+0x14a/0x260 fs/read_write.c:647
 __do_sys_write fs/read_write.c:659 [inline]
 __se_sys_write fs/read_write.c:656 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:656
 x64_sys_call+0x8ef/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 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: 0033:0x7f3880aa0e59
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:00007ffdbd69db78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f3880d19fa0 RCX: 00007f3880aa0e59
RDX: 000000000208e24b RSI: 0000200000000000 RDI: 0000000000000005
RBP: 00007f3880b36e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3880d19fac R14: 00007f3880d19fa0 R15: 00007f3880d19fa0
 </TASK>
==================================================================
BUG: kernel NULL pointer dereference, address: 0000000000000024
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 12cac5067 P4D 12cac5067 PUD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 372 Comm: syz.2.17 Tainted: G    B             syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:arch_atomic_inc fs/f2fs/segment.c:594 [inline]
RIP: 0010:atomic_inc include/linux/atomic/atomic-instrumented.h:182 [inline]
RIP: 0010:f2fs_issue_flush+0x163/0x8b0 fs/f2fs/segment.c:595
Code: 00 31 ff e8 cf c5 51 ff 4c 89 6c 24 10 49 83 c5 24 4c 89 ef be 04 00 00 00 e8 a9 34 91 ff 81 e3 00 04 00 00 0f 85 51 01 00 00 <f0> 41 ff 45 00 4d 8d b7 3c 0c 00 00 4d 89 f5 49 c1 ed 03 48 b8 00
RSP: 0018:ffffc90000c17620 EFLAGS: 00010246
RAX: ffff888110e66200 RBX: 0000000000000000 RCX: ffff888110e662c0
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00000000ffffffff
RBP: ffffc90000c17730 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff0e18c4c R12: 1ffff92000182ecc
R13: 0000000000000024 R14: ffffc90000c17680 R15: ffff88811143c000
FS:  000055556fbcd500(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000024 CR3: 00000001222b1000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 f2fs_do_sync_file+0x11ae/0x1b70 fs/f2fs/file.c:384
 f2fs_sync_file+0x103/0x150 fs/f2fs/file.c:400
 vfs_fsync_range+0x171/0x180 fs/sync.c:188
 generic_write_sync include/linux/fs.h:3038 [inline]
 f2fs_file_write_iter+0x60d/0x29f0 fs/f2fs/file.c:4826
 call_write_iter include/linux/fs.h:2212 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x831/0xfd0 fs/read_write.c:594
 ksys_write+0x14a/0x260 fs/read_write.c:647
 __do_sys_write fs/read_write.c:659 [inline]
 __se_sys_write fs/read_write.c:656 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:656
 x64_sys_call+0x8ef/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 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: 0033:0x7f3880aa0e59
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:00007ffdbd69db78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f3880d19fa0 RCX: 00007f3880aa0e59
RDX: 000000000208e24b RSI: 0000200000000000 RDI: 0000000000000005
RBP: 00007f3880b36e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3880d19fac R14: 00007f3880d19fa0 R15: 00007f3880d19fa0
 </TASK>
Modules linked in:
CR2: 0000000000000024
---[ end trace 269845b78b3bcf24 ]---
RIP: 0010:arch_atomic_inc fs/f2fs/segment.c:594 [inline]
RIP: 0010:atomic_inc include/linux/atomic/atomic-instrumented.h:182 [inline]
RIP: 0010:f2fs_issue_flush+0x163/0x8b0 fs/f2fs/segment.c:595
Code: 00 31 ff e8 cf c5 51 ff 4c 89 6c 24 10 49 83 c5 24 4c 89 ef be 04 00 00 00 e8 a9 34 91 ff 81 e3 00 04 00 00 0f 85 51 01 00 00 <f0> 41 ff 45 00 4d 8d b7 3c 0c 00 00 4d 89 f5 49 c1 ed 03 48 b8 00
RSP: 0018:ffffc90000c17620 EFLAGS: 00010246
RAX: ffff888110e66200 RBX: 0000000000000000 RCX: ffff888110e662c0
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00000000ffffffff
RBP: ffffc90000c17730 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff0e18c4c R12: 1ffff92000182ecc
R13: 0000000000000024 R14: ffffc90000c17680 R15: ffff88811143c000
FS:  000055556fbcd500(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000024 CR3: 00000001222b1000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	00 31                	add    %dh,(%rcx)
   2:	ff                   	ljmp   (bad)
   3:	e8 cf c5 51 ff       	call   0xff51c5d7
   8:	4c 89 6c 24 10       	mov    %r13,0x10(%rsp)
   d:	49 83 c5 24          	add    $0x24,%r13
  11:	4c 89 ef             	mov    %r13,%rdi
  14:	be 04 00 00 00       	mov    $0x4,%esi
  19:	e8 a9 34 91 ff       	call   0xff9134c7
  1e:	81 e3 00 04 00 00    	and    $0x400,%ebx
  24:	0f 85 51 01 00 00    	jne    0x17b
* 2a:	f0 41 ff 45 00       	lock incl 0x0(%r13) <-- trapping instruction
  2f:	4d 8d b7 3c 0c 00 00 	lea    0xc3c(%r15),%r14
  36:	4d 89 f5             	mov    %r14,%r13
  39:	49 c1 ed 03          	shr    $0x3,%r13
  3d:	48                   	rex.W
  3e:	b8                   	.byte 0xb8

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/28 05:47 android13-5.15-lts c85054db4618 fb92f11c .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (corrupt fs)] ci2-android-5-15 KASAN: null-ptr-deref Write in f2fs_issue_flush
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.