divide error in block2mtd_setup2

Status: upstream: reported on 2026/08/10 00:34
Subsystems: mtd
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+b320a4d5f65a61dbbf89@syzkaller.appspotmail.com
First crash: 6d05h, last: 6d05h
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
6092b509 repro-c Reproduced: ✅
❓ divide error in block2mtd_setup2 2026/08/10 07:48 2026/08/10 07:48 2026/08/10 07:56 5d63f80b
7c0d9f2e assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ divide error in block2mtd_setup2 2026/08/09 16:38 2026/08/09 16:38 2026/08/09 17:07 5d63f80b
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[syzbot] [mtd?] divide error in block2mtd_setup2 4 (5) 2026/08/10 16:27
[PATCH] mtd: block2mtd: Fix divide error when erase_size is zero 1 (1) 2026/08/10 09:12
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 divide error in block2mtd_setup2 2 syz, C 10 3d14h 13d 0/3 upstream: reported C repro on 2026/07/28 09:32
▶ ▼ Last patch testing requests (3)
Created Duration User Patch Repo Result
2026/08/10 17:41 20m nogikh@google.com upstream error
2026/08/10 12:41 23m nogikh@google.com upstream error
2026/08/10 08:58 27m nogikh@google.com upstream error

Sample crash report:
Oops: divide error: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5325 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:add_device drivers/mtd/devices/block2mtd.c:296 [inline]
RIP: 0010:block2mtd_setup2+0x592/0xda0 drivers/mtd/devices/block2mtd.c:459
Code: 48 8b 74 24 30 48 63 ce 48 89 d8 48 09 c8 48 c1 e8 20 4c 8b 64 24 10 74 0d 48 89 d8 48 99 48 f7 f9 49 89 d5 eb 09 89 d8 31 d2 <f7> f6 41 89 d5 31 ff 4c 89 ee e8 1f da 39 fb 4d 85 ed 0f 85 90 04
RSP: 0018:ffffc9000f26f9a0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001f00000
RBP: ffffc9000f26fb98 R08: ffff8880353962ef R09: 1ffff11006a72c5d
R10: dffffc0000000000 R11: ffffed1006a72c5e R12: 0000000000000000
R13: ffff88801d02d0b4 R14: ffff8880122be000 R15: ffff8880122be000
FS:  00007fa7d8c5d6c0(0000) GS:ffff88808c540000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa7d801bb30 CR3: 000000003fb3c000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 block2mtd_setup+0x27/0xe0 drivers/mtd/devices/block2mtd.c:476
 param_attr_store+0x214/0x310 kernel/params.c:589
 module_attr_store+0x65/0x90 kernel/params.c:904
 kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x612/0xba0 fs/read_write.c:687
 ksys_write+0x150/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa7d7d9e019
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:00007fa7d8c5cfe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fa7d8025fa0 RCX: 00007fa7d7d9e019
RDX: 000000000000000c RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007fa7d7e3500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa7d8026038 R14: 00007fa7d8025fa0 R15: 00007ffe5587a628
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:add_device drivers/mtd/devices/block2mtd.c:296 [inline]
RIP: 0010:block2mtd_setup2+0x592/0xda0 drivers/mtd/devices/block2mtd.c:459
Code: 48 8b 74 24 30 48 63 ce 48 89 d8 48 09 c8 48 c1 e8 20 4c 8b 64 24 10 74 0d 48 89 d8 48 99 48 f7 f9 49 89 d5 eb 09 89 d8 31 d2 <f7> f6 41 89 d5 31 ff 4c 89 ee e8 1f da 39 fb 4d 85 ed 0f 85 90 04
RSP: 0018:ffffc9000f26f9a0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001f00000
RBP: ffffc9000f26fb98 R08: ffff8880353962ef R09: 1ffff11006a72c5d
R10: dffffc0000000000 R11: ffffed1006a72c5e R12: 0000000000000000
R13: ffff88801d02d0b4 R14: ffff8880122be000 R15: ffff8880122be000
FS:  00007fa7d8c5d6c0(0000) GS:ffff88808c540000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffee237bf52 CR3: 000000003fb3c000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess):
   0:	48 8b 74 24 30       	mov    0x30(%rsp),%rsi
   5:	48 63 ce             	movslq %esi,%rcx
   8:	48 89 d8             	mov    %rbx,%rax
   b:	48 09 c8             	or     %rcx,%rax
   e:	48 c1 e8 20          	shr    $0x20,%rax
  12:	4c 8b 64 24 10       	mov    0x10(%rsp),%r12
  17:	74 0d                	je     0x26
  19:	48 89 d8             	mov    %rbx,%rax
  1c:	48 99                	cqto
  1e:	48 f7 f9             	idiv   %rcx
  21:	49 89 d5             	mov    %rdx,%r13
  24:	eb 09                	jmp    0x2f
  26:	89 d8                	mov    %ebx,%eax
  28:	31 d2                	xor    %edx,%edx
* 2a:	f7 f6                	div    %esi <-- trapping instruction
  2c:	41 89 d5             	mov    %edx,%r13d
  2f:	31 ff                	xor    %edi,%edi
  31:	4c 89 ee             	mov    %r13,%rsi
  34:	e8 1f da 39 fb       	call   0xfb39da58
  39:	4d 85 ed             	test   %r13,%r13
  3c:	0f                   	.byte 0xf
  3d:	85                   	.byte 0x85
  3e:	90                   	nop
  3f:	04                   	.byte 0x4

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/04 13:42 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root divide error in block2mtd_setup2
* Struck through repros no longer work on HEAD.