BUG: unable to handle kernel NULL pointer dereference in z_erofs_decompress

Status: upstream: reported C repro on 2026/05/06 08:21
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+e407c0ff6d2436109ecb@syzkaller.appspotmail.com
First crash: 94d, last: 37d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/05/27 lts (merge base) 93741761e5e3 C [report] lost connection to test machine
2026/05/27 upstream (ToT) eb3f4b7426cf C [report] lost connection to test machine
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 BUG: unable to handle kernel NULL pointer dereference in z_erofs_decompress 10 syz, C 6 30d 222d 0/2 upstream: reported C repro on 2025/12/29 07:00

Sample crash report:
loop2: detected capacity change from 0 to 16
erofs: (device loop2): mounted with root inode @ nid 36.
erofs: (device loop2): z_erofs_extent_lookback: bogus lookback distance @ nid 36
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 12ee48067 P4D 12ee48067 PUD 0 
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 371 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc90000ab6d88 EFLAGS: 00010246
RAX: 1ffffffff0ac1532 RBX: ffffc90000ab76e0 RCX: ffff88811b8f62c0
RDX: 0000000000000000 RSI: ffffc90000ab76e0 RDI: ffffc90000ab7240
RBP: ffffc90000ab6db0 R08: ffffc90000ab726f R09: ffffc90000ab726a
R10: dffffc0000000000 R11: fffff52000156e4e R12: dffffc0000000000
R13: 000000000000073b R14: ffffc90000ab7240 R15: ffffffff8560a990
FS:  000055555c736500(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000012ee58000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 z_erofs_decompress+0x79/0xb0 fs/erofs/decompressor.c:360
 z_erofs_decompress_pcluster fs/erofs/zdata.c:1113 [inline]
 z_erofs_decompress_queue+0x1100/0x19e0 fs/erofs/zdata.c:1191
 z_erofs_runqueue+0x116d/0x11f0 fs/erofs/zdata.c:-1
 z_erofs_readpage+0x25d/0x4d0 fs/erofs/zdata.c:1604
 do_read_cache_page+0x58e/0xb10 mm/filemap.c:-1
 read_cache_page+0x50/0x70 mm/filemap.c:3676
 read_mapping_page include/linux/pagemap.h:513 [inline]
 find_target_block_classic fs/erofs/namei.c:104 [inline]
 erofs_namei+0x12a/0xf80 fs/erofs/namei.c:184
 erofs_lookup+0xa5/0x260 fs/erofs/namei.c:228
 __lookup_slow+0x2b8/0x410 fs/namei.c:1671
 lookup_slow+0x57/0x70 fs/namei.c:1688
 walk_component+0x326/0x460 fs/namei.c:1984
 link_path_walk+0x688/0xde0 fs/namei.c:-1
 path_parentat fs/namei.c:2510 [inline]
 __filename_parentat+0x254/0x690 fs/namei.c:2534
 filename_parentat fs/namei.c:2552 [inline]
 filename_create+0xd5/0x440 fs/namei.c:3824
 do_mkdirat+0x5c/0x4d0 fs/namei.c:4088
 __do_sys_mkdir fs/namei.c:4118 [inline]
 __se_sys_mkdir fs/namei.c:4116 [inline]
 __x64_sys_mkdir+0x6e/0x80 fs/namei.c:4116
 x64_sys_call+0x124/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:84
 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: 0033:0x7f253636ce59
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:00007ffd1e96f568 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 00007f25365f4fa0 RCX: 00007f253636ce59
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000000
RBP: 00007f2536402e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f25365f4fac R14: 00007f25365f4fa0 R15: 00007f25365f4fa0
 </TASK>
Modules linked in:
CR2: 0000000000000000
---[ end trace 22711f19847065a3 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc90000ab6d88 EFLAGS: 00010246
RAX: 1ffffffff0ac1532 RBX: ffffc90000ab76e0 RCX: ffff88811b8f62c0
RDX: 0000000000000000 RSI: ffffc90000ab76e0 RDI: ffffc90000ab7240
RBP: ffffc90000ab6db0 R08: ffffc90000ab726f R09: ffffc90000ab726a
R10: dffffc0000000000 R11: fffff52000156e4e R12: dffffc0000000000
R13: 000000000000073b R14: ffffc90000ab7240 R15: ffffffff8560a990
FS:  000055555c736500(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000012ee58000 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
2026/07/02 17:19 android13-5.15-lts a64de05eba09 2b70b115 .config console 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 z_erofs_decompress
2026/05/06 08:20 android13-5.15-lts e63ebedc51b2 26da2c66 .config console 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 z_erofs_decompress
* Struck through repros no longer work on HEAD.