[syzbot] [overlayfs?] BUG: unable to handle kernel NULL pointer dereference in __lookup_slow (3)

syzbot
2024-04-28T08:01:28Z

Hello,

syzbot found the following issue on:

HEAD commit: 9d1ddab261f3 Merge tag '6.9-rc5-smb-client-fixes' of git:/..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=131e4bf7180000
kernel config: https://syzkaller.appspot.com/x/.config?x=5a05c230e142f2bc
dashboard link: https://syzkaller.appspot.com/bug?extid=94891a5155abdf6821b7
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1514c36f180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13649630980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/de0722c51d76/disk-9d1ddab2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bbe188cbd737/vmlinux-9d1ddab2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/74cb740a2e68/bzImage-9d1ddab2.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/1ea7930b04fb/mount_0.gz

Bisection is inconclusive: the issue happens on the oldest tested release.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=143e0f10980000
final oops: https://syzkaller.appspot.com/x/report.txt?x=163e0f10980000
console output: https://syzkaller.appspot.com/x/log.txt?x=123e0f10980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+94891a5155abdf6821b7@syzkaller.appspotmail.com

overlayfs: fs on './file0' does not support file handles, falling back to index=off,nfs_export=off.
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 8000000022852067 P4D 8000000022852067 PUD 2dc51067 PMD 0
Oops: 0010 [#1] PREEMPT SMP KASAN PTI
CPU: 1 PID: 5070 Comm: syz-executor324 Not tainted 6.9.0-rc5-syzkaller-00036-g9d1ddab261f3 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffffc9000352f1b8 EFLAGS: 00010246
RAX: 1ffffffff17b0bc0 RBX: ffffffff8bd85e00 RCX: ffff88807ef35a00
RDX: 0000000000000000 RSI: ffff8880207f85e0 RDI: ffff88807ebf8018
RBP: ffffc9000352f2d0 R08: ffffffff820b2843 R09: 1ffffffff28ed13f
R10: dffffc0000000000 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff8880207f85e0 R14: 1ffff110040ff0bc R15: 1ffff920006a5e3c
FS: 0000555558bc6380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000001cba8000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__lookup_slow+0x28c/0x3f0 fs/namei.c:1692
lookup_slow fs/namei.c:1709 [inline]
lookup_one_unlocked+0x1a4/0x290 fs/namei.c:2817
ovl_lookup_positive_unlocked fs/overlayfs/namei.c:210 [inline]
ovl_lookup_single+0x200/0xbd0 fs/overlayfs/namei.c:240
ovl_lookup_layer+0x417/0x510 fs/overlayfs/namei.c:333
ovl_lookup+0xcf7/0x2a60 fs/overlayfs/namei.c:1124
lookup_open fs/namei.c:3475 [inline]
open_last_lookups fs/namei.c:3566 [inline]
path_openat+0x1033/0x3240 fs/namei.c:3796
do_filp_open+0x235/0x490 fs/namei.c:3826
do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_openat fs/open.c:1437 [inline]
__se_sys_openat fs/open.c:1432 [inline]
__x64_sys_openat+0x247/0x2a0 fs/open.c:1432
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd739fc9f39
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 17 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc39adcc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 6e69666e6f636e75 RCX: 00007fd739fc9f39
RDX: 0000000000001200 RSI: 0000000020000340 RDI: 0000000000000003
RBP: 646165725f78616d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 7269647265776f6c R14: 0079616c7265766f R15: 2f31656c69662f2e
</TASK>
Modules linked in:
CR2: 0000000000000000
---[ end trace 0000000000000000 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffffc9000352f1b8 EFLAGS: 00010246
RAX: 1ffffffff17b0bc0 RBX: ffffffff8bd85e00 RCX: ffff88807ef35a00
RDX: 0000000000000000 RSI: ffff8880207f85e0 RDI: ffff88807ebf8018
RBP: ffffc9000352f2d0 R08: ffffffff820b2843 R09: 1ffffffff28ed13f
R10: dffffc0000000000 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff8880207f85e0 R14: 1ffff110040ff0bc R15: 1ffff920006a5e3c
FS: 0000555558bc6380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000001cba8000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

---
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