syzbot


BUG: unable to handle kernel paging request in __d_lookup_rcu

Status: upstream: reported syz repro on 2025/02/17 08:04
Subsystems: bcachefs
[Documentation on labels]
Reported-by: syzbot+a3f3ed84ec8cc241ff9e@syzkaller.appspotmail.com
First crash: 4d16h, last: 4d16h
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [bcachefs?] BUG: unable to handle kernel paging request in __d_lookup_rcu 0 (1) 2025/02/17 08:04

Sample crash report:
BUG: unable to handle page fault for address: ffffffffffffffcf
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD e93c067 P4D e93c067 PUD e93e067 PMD 0 
Oops: Oops: 0000 [#1] PREEMPT SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5322 Comm: udevd Not tainted 6.14.0-rc2-syzkaller-00303-gad1b832bf1cf #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:__seqprop_spinlock_sequence include/linux/seqlock.h:227 [inline]
RIP: 0010:__d_lookup_rcu+0x18d/0x490 fs/dcache.c:2264
Code: 00 00 00 00 89 44 24 24 4c 89 6c 24 30 4c 89 7c 24 28 48 8d 7d c8 48 89 f8 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 bb 01 00 00 <44> 8b 75 c8 48 8d 5d 10 48 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08
RSP: 0018:ffffc9000d13f768 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff888042a8cd88 RCX: ffff888000a10000
RDX: 0000000000000000 RSI: ffff888042a8cd78 RDI: ffffffffffffffcf
RBP: 0000000000000007 R08: ffffffff82419fdc R09: 1ffff92000076d24
R10: dffffc0000000000 R11: fffff52000076d25 R12: dffffc0000000000
R13: ffff88801d03fbe8 R14: 0000000000000000 R15: 0000000000000004
FS:  00007fd7f3eb2280(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffcf CR3: 0000000012b1a000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 lookup_fast+0xca/0x590 fs/namei.c:1727
 walk_component fs/namei.c:2110 [inline]
 link_path_walk+0x672/0xea0 fs/namei.c:2479
 path_openat+0x266/0x3590 fs/namei.c:3985
 do_filp_open+0x27f/0x4e0 fs/namei.c:4016
 do_sys_openat2+0x13e/0x1d0 fs/open.c:1428
 do_sys_open fs/open.c:1443 [inline]
 __do_sys_openat fs/open.c:1459 [inline]
 __se_sys_openat fs/open.c:1454 [inline]
 __x64_sys_openat+0x247/0x2a0 fs/open.c:1454
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd7f3f859a4
Code: 24 20 48 8d 44 24 30 48 89 44 24 28 64 8b 04 25 18 00 00 00 85 c0 75 2c 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 76 60 48 8b 15 55 a4 0d 00 f7 d8 64 89 02 48 83
RSP: 002b:00007ffd67ebfd80 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 00007fd7f3f859a4
RDX: 0000000000080000 RSI: 00007ffd67ebfeb8 RDI: 00000000ffffff9c
RBP: 00007ffd67ebfeb8 R08: 0000000000000008 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000080000
R13: 0000562f3212db42 R14: 0000000000000001 R15: 0000562f32149160
 </TASK>
Modules linked in:
CR2: ffffffffffffffcf
---[ end trace 0000000000000000 ]---
RIP: 0010:__seqprop_spinlock_sequence include/linux/seqlock.h:227 [inline]
RIP: 0010:__d_lookup_rcu+0x18d/0x490 fs/dcache.c:2264
Code: 00 00 00 00 89 44 24 24 4c 89 6c 24 30 4c 89 7c 24 28 48 8d 7d c8 48 89 f8 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 bb 01 00 00 <44> 8b 75 c8 48 8d 5d 10 48 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08
RSP: 0018:ffffc9000d13f768 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff888042a8cd88 RCX: ffff888000a10000
RDX: 0000000000000000 RSI: ffff888042a8cd78 RDI: ffffffffffffffcf
RBP: 0000000000000007 R08: ffffffff82419fdc R09: 1ffff92000076d24
R10: dffffc0000000000 R11: fffff52000076d25 R12: dffffc0000000000
R13: ffff88801d03fbe8 R14: 0000000000000000 R15: 0000000000000004
FS:  00007fd7f3eb2280(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffcf CR3: 0000000012b1a000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	00 00                	add    %al,(%rax)
   2:	00 00                	add    %al,(%rax)
   4:	89 44 24 24          	mov    %eax,0x24(%rsp)
   8:	4c 89 6c 24 30       	mov    %r13,0x30(%rsp)
   d:	4c 89 7c 24 28       	mov    %r15,0x28(%rsp)
  12:	48 8d 7d c8          	lea    -0x38(%rbp),%rdi
  16:	48 89 f8             	mov    %rdi,%rax
  19:	48 c1 e8 03          	shr    $0x3,%rax
  1d:	42 0f b6 04 20       	movzbl (%rax,%r12,1),%eax
  22:	84 c0                	test   %al,%al
  24:	0f 85 bb 01 00 00    	jne    0x1e5
* 2a:	44 8b 75 c8          	mov    -0x38(%rbp),%r14d <-- trapping instruction
  2e:	48 8d 5d 10          	lea    0x10(%rbp),%rbx
  32:	48 89 d8             	mov    %rbx,%rax
  35:	48 c1 e8 03          	shr    $0x3,%rax
  39:	42 80 3c 20 00       	cmpb   $0x0,(%rax,%r12,1)
  3e:	74 08                	je     0x48

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/02/16 13:03 upstream ad1b832bf1cf 40a34ec9 .config console log report syz / log [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root BUG: unable to handle kernel paging request in __d_lookup_rcu
* Struck through repros no longer work on HEAD.