linux-kernel - [BUG] f2fs: divide error in f2fs_all_cluster_page

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Message-ID: <44D8F7B3-68AD-425F-9915-65D27591F93F@psu.edu>
Date: Sun, 12 Oct 2025 23:49:43 +0000
From: "Bai, Shuangpeng" <SJB7183@....EDU>
To: "jaegeuk@...nel.org" <jaegeuk@...nel.org>, "chao@...nel.org"
	<chao@...nel.org>
CC: "linux-f2fs-devel@...ts.sourceforge.net"
	<linux-f2fs-devel@...ts.sourceforge.net>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "syzkaller@...glegroups.com"
	<syzkaller@...glegroups.com>
Subject: [BUG] f2fs: divide error in f2fs_all_cluster_page_ready on v6.17

Hi Kernel Maintainers,

Our tool found a new kernel bug "divide error in f2fs_all_cluster_page_ready". Please see the details below.

Kernel commit: 6.17
Kernel config: attachment
Reproducer: attachment

The reproducer triggers the crash reliably in ~500 seconds on a QEMU x86_64 VM. 

I’m happy to test debug patches or provide additional information.


Oops: divide error: 0000 [#1] SMP KASAN PTI
CPU: 0 UID: 0 PID: 11441 Comm: syz.0.46 Not tainted 6.17.0 #1 PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:f2fs_all_cluster_page_ready+0x106/0x550 fs/f2fs/compress.c:857
Code: 00 8b 4d 00 48 89 d8 48 c1 e8 20 74 19 48 89 d8 31 d2 48 f7 f1 48 89 d5 eb 14 48 89 5c 24 10 e8 40 a4 6d fd eb 2d 89 d8 31 d2 <f7> f1 89 d5 31 ff 48 89 ee e8 0c a9 6d fd 48 85 ed 74 0c e8 22 a4
RSP: 0018:ffffc90006616e60 EFLAGS: 00010246
RAX: 0000000000000003 RBX: 0000000000000003 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90006617270 R08: ffffffff84552d26 R09: 0000000000000000
R10: ffff888155ad2000 R11: ffffffff81d2aa26 R12: 0000000000000001
R13: dffffc0000000000 R14: 0000000000000010 R15: ffffc90006617260
FS:  00007f8bac5b5640(0000) GS:ffff888220f02000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056508a326000 CR3: 0000000117bec000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 f2fs_write_cache_pages fs/f2fs/data.c:3078 [inline]
 __f2fs_write_data_pages fs/f2fs/data.c:3290 [inline]
 f2fs_write_data_pages+0x1c19/0x3600 fs/f2fs/data.c:3317
 do_writepages+0x38e/0x640 mm/page-writeback.c:2634
 filemap_fdatawrite_wbc mm/filemap.c:386 [inline]
 __filemap_fdatawrite_range mm/filemap.c:419 [inline]
 file_write_and_wait_range+0x2ba/0x3e0 mm/filemap.c:794
 f2fs_do_sync_file+0x6e6/0x1b00 fs/f2fs/file.c:294
 generic_write_sync include/linux/fs.h:3043 [inline]
 f2fs_file_write_iter+0x76e/0x2700 fs/f2fs/file.c:5259
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x7e9/0xe00 fs/read_write.c:686
 ksys_write+0x19d/0x2d0 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf7/0x470 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8bab7ae49d
Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8bac5b4f98 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f8baba26180 RCX: 00007f8bab7ae49d
RDX: 000000000000ffbd RSI: 0000200000000240 RDI: 0000000000000007
RBP: 00007f8bab848268 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8baba26218 R14: 00007f8baba26180 R15: 00007f8bac595000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:f2fs_all_cluster_page_ready+0x106/0x550 fs/f2fs/compress.c:857
Code: 00 8b 4d 00 48 89 d8 48 c1 e8 20 74 19 48 89 d8 31 d2 48 f7 f1 48 89 d5 eb 14 48 89 5c 24 10 e8 40 a4 6d fd eb 2d 89 d8 31 d2 <f7> f1 89 d5 31 ff 48 89 ee e8 0c a9 6d fd 48 85 ed 74 0c e8 22 a4
RSP: 0018:ffffc90006616e60 EFLAGS: 00010246
RAX: 0000000000000003 RBX: 0000000000000003 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90006617270 R08: ffffffff84552d26 R09: 0000000000000000
R10: ffff888155ad2000 R11: ffffffff81d2aa26 R12: 0000000000000001
R13: dffffc0000000000 R14: 0000000000000010 R15: ffffc90006617260
FS:  00007f8bac5b5640(0000) GS:ffff888220f02000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056508a326000 CR3: 0000000117bec000 CR4: 00000000000006f0
----------------
Code disassembly (best guess):
   0:	00 8b 4d 00 48 89    	add    %cl,-0x76b7ffb3(%rbx)
   6:	d8 48 c1             	fmuls  -0x3f(%rax)
   9:	e8 20 74 19 48       	call   0x4819742e
   e:	89 d8                	mov    %ebx,%eax
  10:	31 d2                	xor    %edx,%edx
  12:	48 f7 f1             	div    %rcx
  15:	48 89 d5             	mov    %rdx,%rbp
  18:	eb 14                	jmp    0x2e
  1a:	48 89 5c 24 10       	mov    %rbx,0x10(%rsp)
  1f:	e8 40 a4 6d fd       	call   0xfd6da464
  24:	eb 2d                	jmp    0x53
  26:	89 d8                	mov    %ebx,%eax
  28:	31 d2                	xor    %edx,%edx
* 2a:	f7 f1                	div    %ecx <-- trapping instruction
  2c:	89 d5                	mov    %edx,%ebp
  2e:	31 ff                	xor    %edi,%edi
  30:	48 89 ee             	mov    %rbp,%rsi
  33:	e8 0c a9 6d fd       	call   0xfd6da944
  38:	48 85 ed             	test   %rbp,%rbp
  3b:	74 0c                	je     0x49
  3d:	e8                   	.byte 0xe8
  3e:	22                   	.byte 0x22
  3f:	a4                   	movsb  %ds:(%rsi),%es:(%rdi)

Best,
Shuangpeng


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