syzbot
BUG: unable to handle kernel paging request in snapshot_merge_next_chunks
Status:
premoderation: reported C repro on 2026/10/31 01:55
Reported-by: syzbot+7adf42c3c3eca837096d@syzkaller.appspotmail.com
First crash: 1d04h, last: 1d03h
Sample crash report:
BUG: unable to handle page fault for address: fffffffffffffff1
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 7cae067 P4D 7cae067
PUD 7cb0067 PMD 0
Oops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 0 UID: 0 PID: 312 Comm: syz-executor138 Not tainted syzkaller #0 04b5f10b80d13b0533bf6aaa302b886c75cf6d37
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
RIP: 0010:snapshot_merge_next_chunks+0x270/0xcb0 drivers/md/dm-snap.c:1057
Code: 83 c3 38 48 89 d8 48 c1 e8 03 80 3c 08 00 74 08 48 89 df e8 62 7d df fd 4c 8b 1b 4c 89 ff 4c 89 e6 4c 89 ea 41 ba 9e 71 80 50 <45> 03 53 f1 74 02 0f 0b 2e e8 82 e3 fd 1b 89 c3 bf 01 00 00 00 89
RSP: 0018:ffffc900011ef8a0 EFLAGS: 00010246
RAX: 1ffffffff1062c8f RBX: ffffffff88316478 RCX: dffffc0000000000
RDX: ffffc900011ef940 RSI: ffffc900011ef920 RDI: ffff888105790400
RBP: ffffc900011efa90 R08: ffff888104f629bf R09: 1ffff110209ec537
R10: 000000005080719e R11: 0000000000000000 R12: ffffc900011ef920
R13: ffffc900011ef940 R14: ffff888104f629b8 R15: ffff888105790400
FS: 000055557219c3c0(0000) GS:ffff8881f6c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffffffffff1 CR3: 0000000106be2000 CR4: 00000000003526b0
Call Trace:
<TASK>
start_merge drivers/md/dm-snap.c:1167 [inline]
snapshot_merge_resume+0x256/0x2b0 drivers/md/dm-snap.c:2307
dm_table_resume_targets+0x23c/0x380 drivers/md/dm-table.c:2041
__dm_resume+0x25/0x1b0 drivers/md/dm.c:3097
dm_resume+0x16a/0x1f0 drivers/md/dm.c:3143
do_resume drivers/md/dm-ioctl.c:1224 [inline]
dev_suspend+0x3ff/0x700 drivers/md/dm-ioctl.c:1256
ctl_ioctl drivers/md/dm-ioctl.c:2107 [inline]
dm_ctl_ioctl+0x8f3/0xde0 drivers/md/dm-ioctl.c:2129
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:906 [inline]
__se_sys_ioctl+0x123/0x1b0 fs/ioctl.c:892
__x64_sys_ioctl+0x7f/0xa0 fs/ioctl.c:892
x64_sys_call+0x1878/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:17
do_syscall_x64 arch/x86/entry/common.c:47 [inline]
do_syscall_64+0x57/0xf0 arch/x86/entry/common.c:78
entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7fd429835ff9
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff72021f58 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fff72022088 RCX: 00007fd429835ff9
RDX: 0000200000000980 RSI: 00000000c138fd06 RDI: 0000000000000003
RBP: 0000000000000001 R08: 00007fff72022088 R09: 00007fff72022088
R10: 0000000000000013 R11: 0000000000000246 R12: 00007fff72022078
R13: 0000000000000002 R14: 00007fd4298c6ca0 R15: 0000000000000002
</TASK>
Modules linked in:
CR2: fffffffffffffff1
---[ end trace 0000000000000000 ]---
RIP: 0010:snapshot_merge_next_chunks+0x270/0xcb0 drivers/md/dm-snap.c:1057
Code: 83 c3 38 48 89 d8 48 c1 e8 03 80 3c 08 00 74 08 48 89 df e8 62 7d df fd 4c 8b 1b 4c 89 ff 4c 89 e6 4c 89 ea 41 ba 9e 71 80 50 <45> 03 53 f1 74 02 0f 0b 2e e8 82 e3 fd 1b 89 c3 bf 01 00 00 00 89
RSP: 0018:ffffc900011ef8a0 EFLAGS: 00010246
RAX: 1ffffffff1062c8f RBX: ffffffff88316478 RCX: dffffc0000000000
RDX: ffffc900011ef940 RSI: ffffc900011ef920 RDI: ffff888105790400
RBP: ffffc900011efa90 R08: ffff888104f629bf R09: 1ffff110209ec537
R10: 000000005080719e R11: 0000000000000000 R12: ffffc900011ef920
R13: ffffc900011ef940 R14: ffff888104f629b8 R15: ffff888105790400
FS: 000055557219c3c0(0000) GS:ffff8881f6c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffffffffff1 CR3: 0000000106be2000 CR4: 00000000003526b0
----------------
Code disassembly (best guess):
0: 83 c3 38 add $0x38,%ebx
3: 48 89 d8 mov %rbx,%rax
6: 48 c1 e8 03 shr $0x3,%rax
a: 80 3c 08 00 cmpb $0x0,(%rax,%rcx,1)
e: 74 08 je 0x18
10: 48 89 df mov %rbx,%rdi
13: e8 62 7d df fd call 0xfddf7d7a
18: 4c 8b 1b mov (%rbx),%r11
1b: 4c 89 ff mov %r15,%rdi
1e: 4c 89 e6 mov %r12,%rsi
21: 4c 89 ea mov %r13,%rdx
24: 41 ba 9e 71 80 50 mov $0x5080719e,%r10d
* 2a: 45 03 53 f1 add -0xf(%r11),%r10d <-- trapping instruction
2e: 74 02 je 0x32
30: 0f 0b ud2
32: 2e e8 82 e3 fd 1b cs call 0x1bfde3ba
38: 89 c3 mov %eax,%ebx
3a: bf 01 00 00 00 mov $0x1,%edi
3f: 89 .byte 0x89
* Struck through repros no longer work on HEAD.