BUG: unable to handle kernel NULL pointer dereference in __lookup_slow

Status: upstream: reported C repro on 2026/04/18 02:32
Bug presence: origin:downstream
[Documentation on labels]
Reported-by: syzbot+b335889a8d156d1cad3f@syzkaller.appspotmail.com
First crash: 153d, last: 24d
Fix bisection: failed (error log, bisect log)
  
Bug presence (3)
Date Name Commit Repro Result
2026/04/18 android13-5.15-lts (ToT) 7fad219d720d C [report] BUG: unable to handle kernel NULL pointer dereference in __lookup_slow
2026/04/18 lts (merge base) 91d48252ad4b C Didn't crash
2026/04/18 upstream (ToT) eb5249b12507 C Didn't crash
Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream BUG: unable to handle kernel NULL pointer dereference in __lookup_slow fs 10 syz, C inconclusive done 3 2041d 2181d 19/29 fixed on 2021/03/10 01:48
linux-4.19 BUG: unable to handle kernel NULL pointer dereference in __lookup_slow (2) 10 syz, C done 15 1863d 1986d 1/1 fixed on 2021/09/13 16:54
linux-5.15 BUG: unable to handle kernel NULL pointer dereference in __lookup_slow origin:lts-only 10 syz, C done 5 655d 663d 0/3 auto-obsoleted due to no activity on 2025/03/12 04:53
upstream BUG: unable to handle kernel NULL pointer dereference in __lookup_slow (2) fs 10 syz, C inconclusive 4 1901d 1984d 0/29 auto-obsoleted due to no activity on 2023/04/14 10:28
linux-4.19 BUG: unable to handle kernel NULL pointer dereference in __lookup_slow 10 syz, C done 23 2020d 2178d 1/1 fixed on 2021/04/10 11:48
upstream BUG: unable to handle kernel NULL pointer dereference in __lookup_slow (3) overlayfs 10 syz, C inconclusive done 135 665d 873d 0/29 auto-obsoleted due to no activity on 2025/01/31 21:09
android-5-10 BUG: unable to handle kernel NULL pointer dereference in __lookup_slow 10 syz, C 2 15d 257d 0/2 upstream: reported C repro on 2026/01/03 23:57
android-6-1 BUG: unable to handle kernel paging request in __lookup_slow origin:downstream 8 syz, C error 1 134d 138d 0/2 upstream: reported C repro on 2026/05/03 18:11
Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/08/09 11:24 15m retest repro android13-5.15-lts report log

Sample crash report:
exFAT-fs (loop0): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
exFAT-fs (loop0): Medium has reported failures. Some data may be lost.
exFAT-fs (loop0): failed to load upcase table (idx : 0x00010000, chksum : 0xe62de5da, utbl_chksum : 0xe619d30d)
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 0 P4D 0 
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 304 Comm: syz-executor135 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc900009879d8 EFLAGS: 00010246
RAX: 1ffffffff0aa0d90 RBX: 1ffff110244cebba RCX: ffff888124a1a780
RDX: 0000000000000000 RSI: ffff888122675dd0 RDI: ffff8881225cd210
RBP: ffffc90000987ab0 R08: ffffffff87121fef R09: 1ffffffff0e243fd
R10: dffffc0000000000 R11: fffffbfff0e243fe R12: dffffc0000000000
R13: ffff888122675dd0 R14: ffffffff85506c80 R15: 1ffff92000130f40
FS:  000055559358e480(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 0000000125ea4000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __lookup_slow+0x2b8/0x410 fs/namei.c:1671
 lookup_one_len+0x19d/0x2d0 fs/namei.c:2726
 incfs_lookup_dentry+0x60/0xb0 fs/incfs/data_mgmt.c:210
 ioctl_create_file fs/incfs/pseudo_files.c:556 [inline]
 pending_reads_dispatch_ioctl+0x1618/0x1e60 fs/incfs/pseudo_files.c:1030
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:860
 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:860
 x64_sys_call+0x2f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
 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: 0033:0x7f2121974c89
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:00007fff87d31318 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f21219d41b9 RCX: 00007f2121974c89
RDX: 00002000000000c0 RSI: 00000000c058671e RDI: 0000000000000005
RBP: 00007f21219d4189 R08: 00007f21219d5e3d R09: 00007f21219d5e3d
R10: 00007f21219d5e3d R11: 0000000000000246 R12: 00007f21219d5e3d
R13: 00007f21219d40f1 R14: 00007f2121a01bc0 R15: 0000000000000002
 </TASK>
Modules linked in:
CR2: 0000000000000000
---[ end trace ea16d515ab103789 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc900009879d8 EFLAGS: 00010246
RAX: 1ffffffff0aa0d90 RBX: 1ffff110244cebba RCX: ffff888124a1a780
RDX: 0000000000000000 RSI: ffff888122675dd0 RDI: ffff8881225cd210
RBP: ffffc90000987ab0 R08: ffffffff87121fef R09: 1ffffffff0e243fd
R10: dffffc0000000000 R11: fffffbfff0e243fe R12: dffffc0000000000
R13: ffff888122675dd0 R14: ffffffff85506c80 R15: 1ffff92000130f40
FS:  000055559358e480(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 0000000125ea4000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/25 04:49 android13-5.15-lts 2d18a4de3623 614e416a .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 BUG: unable to handle kernel NULL pointer dereference in __lookup_slow
2026/04/18 02:30 android13-5.15-lts 7fad219d720d 24ecfc1e .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (clean fs)] ci2-android-5-15 BUG: unable to handle kernel NULL pointer dereference in __lookup_slow
* Struck through repros no longer work on HEAD.