[v5.15] BUG: unable to handle kernel NULL pointer dereference in __lookup_slow

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0a51d2d4527b Linux 5.15.173
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16980778580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f63d146f1af4415a
dashboard link: https://syzkaller.appspot.com/bug?extid=9db6b2a6346d266bd206
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/733a95526889/disk-0a51d2d4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/409603e5dc40/vmlinux-0a51d2d4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2d60efa369ee/bzImage-0a51d2d4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9db6b2...@syzkaller.appspotmail.com

loop3: detected capacity change from 0 to 64
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 7bdb1067 P4D 7bdb1067 PUD 645a8067 PMD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 26877 Comm: syz.3.4579 Not tainted 5.15.173-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc90003647318 EFLAGS: 00010246
RAX: 1ffffffff152df28 RBX: ffffffff8a96f940 RCX: 0000000000080000
RDX: 0000000000000000 RSI: ffff88807497eeb0 RDI: ffff8880517a0018
RBP: ffffc90003647430 R08: ffffffff81d86ead R09: fffffbfff2d1a800
R10: 0000000000000000 R11: dffffc0000000001 R12: dffffc0000000000
R13: ffff88807497eeb0 R14: 1ffff1100e92fdd6 R15: 1ffff920006c8e68
FS: 00007f47c1fa46c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000000246a5000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__lookup_slow+0x275/0x3d0 fs/namei.c:1663
lookup_slow fs/namei.c:1680 [inline]
lookup_one_unlocked+0x19c/0x280 fs/namei.c:2779
ovl_lookup_positive_unlocked fs/overlayfs/namei.c:205 [inline]
ovl_lookup_single+0x62/0x840 fs/overlayfs/namei.c:230
ovl_lookup_layer+0x413/0x510 fs/overlayfs/namei.c:314
ovl_lookup+0xb77/0x1f10 fs/overlayfs/namei.c:914
lookup_open fs/namei.c:3440 [inline]
open_last_lookups fs/namei.c:3532 [inline]
path_openat+0x111d/0x2f20 fs/namei.c:3739
do_filp_open+0x21c/0x460 fs/namei.c:3769
do_sys_openat2+0x13b/0x4f0 fs/open.c:1253
do_sys_open fs/open.c:1269 [inline]
__do_sys_openat fs/open.c:1285 [inline]
__se_sys_openat fs/open.c:1280 [inline]
__x64_sys_openat+0x243/0x290 fs/open.c:1280
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f47c412c819
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f47c1fa4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f47c42e3fa0 RCX: 00007f47c412c819
RDX: 0000000000000000 RSI: 0000000020000040 RDI: ffffffffffffff9c
RBP: 00007f47c419f75e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f47c42e3fa0 R15: 00007fffc459a838
</TASK>
Modules linked in:
CR2: 0000000000000000
---[ end trace b8752512013ceba1 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc90003647318 EFLAGS: 00010246

RAX: 1ffffffff152df28 RBX: ffffffff8a96f940 RCX: 0000000000080000
RDX: 0000000000000000 RSI: ffff88807497eeb0 RDI: ffff8880517a0018
RBP: ffffc90003647430 R08: ffffffff81d86ead R09: fffffbfff2d1a800
R10: 0000000000000000 R11: dffffc0000000001 R12: dffffc0000000000
R13: ffff88807497eeb0 R14: 1ffff1100e92fdd6 R15: 1ffff920006c8e68
FS: 00007f47c1fa46c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000000246a5000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 0a51d2d4527b Linux 5.15.173
git tree: linux-5.15.y

console output: https://syzkaller.appspot.com/x/log.txt?x=108c0778580000

kernel config: https://syzkaller.appspot.com/x/.config?x=f63d146f1af4415a
dashboard link: https://syzkaller.appspot.com/bug?extid=9db6b2a6346d266bd206
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=17320530580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10d476e8580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/733a95526889/disk-0a51d2d4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/409603e5dc40/vmlinux-0a51d2d4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2d60efa369ee/bzImage-0a51d2d4.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/4795688e11ea/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9db6b2...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 64

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page

PGD 2ab3d067 P4D 2ab3d067 PUD 2ab3a067 PMD 0

Oops: 0010 [#1] PREEMPT SMP KASAN

CPU: 1 PID: 4161 Comm: syz-executor213 Not tainted 5.15.173-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.

RSP: 0018:ffffc900011df318 EFLAGS: 00010246
RAX: 1ffffffff152df28 RBX: ffffffff8a96f940 RCX: ffff88807def5940
RDX: 0000000000000000 RSI: ffff8880758dbbe8 RDI: ffff888075be0018
RBP: ffffc900011df430 R08: ffffffff81d86ead R09: fffffbfff2d1a589

R10: 0000000000000000 R11: dffffc0000000001 R12: dffffc0000000000

R13: ffff8880758dbbe8 R14: 1ffff1100eb1b77d R15: 1ffff9200023be68
FS: 00005555669f2380(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: ffffffffffffffd6 CR3: 0000000025027000 CR4: 00000000003506e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__lookup_slow+0x275/0x3d0 fs/namei.c:1663
lookup_slow fs/namei.c:1680 [inline]
lookup_one_unlocked+0x19c/0x280 fs/namei.c:2779
ovl_lookup_positive_unlocked fs/overlayfs/namei.c:205 [inline]
ovl_lookup_single+0x62/0x840 fs/overlayfs/namei.c:230
ovl_lookup_layer+0x413/0x510 fs/overlayfs/namei.c:314
ovl_lookup+0xb77/0x1f10 fs/overlayfs/namei.c:914
lookup_open fs/namei.c:3440 [inline]
open_last_lookups fs/namei.c:3532 [inline]
path_openat+0x111d/0x2f20 fs/namei.c:3739
do_filp_open+0x21c/0x460 fs/namei.c:3769
do_sys_openat2+0x13b/0x4f0 fs/open.c:1253
do_sys_open fs/open.c:1269 [inline]
__do_sys_openat fs/open.c:1285 [inline]
__se_sys_openat fs/open.c:1280 [inline]
__x64_sys_openat+0x243/0x290 fs/open.c:1280
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7fa67fc2a709
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:00007ffc79ff3558 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 00007fa67fc2a709

RDX: 0000000000000000 RSI: 0000000020000040 RDI: ffffffffffffff9c

RBP: 00007fa67fc9d610 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffc79ff3728 R14: 0000000000000001 R15: 0000000000000001

</TASK>
Modules linked in:
CR2: 0000000000000000

---[ end trace 270e02963b30c3ba ]---

RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.

RSP: 0018:ffffc900011df318 EFLAGS: 00010246
RAX: 1ffffffff152df28 RBX: ffffffff8a96f940 RCX: ffff88807def5940
RDX: 0000000000000000 RSI: ffff8880758dbbe8 RDI: ffff888075be0018
RBP: ffffc900011df430 R08: ffffffff81d86ead R09: fffffbfff2d1a589

R10: 0000000000000000 R11: dffffc0000000001 R12: dffffc0000000000

R13: ffff8880758dbbe8 R14: 1ffff1100eb1b77d R15: 1ffff9200023be68
FS: 00005555669f2380(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: ffffffffffffffd6 CR3: 0000000025027000 CR4: 00000000003506e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

[syzbot]

syzbot suspects this issue could be fixed by backporting the following commit:

commit c8b359dddb418c60df1a69beea01d1b3322bfe83
git tree: upstream
Author: Vasiliy Kovalev <kov...@altlinux.org>
Date: Tue Nov 19 15:58:17 2024 +0000

ovl: Filter invalid inodes with missing lookup function

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=175acd44580000

kernel config: https://syzkaller.appspot.com/x/.config?x=f63d146f1af4415a
dashboard link: https://syzkaller.appspot.com/bug?extid=9db6b2a6346d266bd206

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1180e9c0580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=147b575f980000


Please keep in mind that other backports might be required as well.

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[syzbot]

The commit that was suspected to fix the issue was backported to the fuzzed
kernel trees.

commit 749eac5a6687ec99116e0691d0d71225254654e3
Author: <kov...@altlinux.org>

Date: Tue Nov 19 15:58:17 2024 +0000

ovl: Filter invalid inodes with missing lookup function

If you believe this is correct, please reply with
#syz fix: ovl: Filter invalid inodes with missing lookup function

The commit was initially detected here:

commit c8b359dddb418c60df1a69beea01d1b3322bfe83
git tree: upstream
Author: Vasiliy Kovalev <kov...@altlinux.org>
Date: Tue Nov 19 15:58:17 2024 +0000

ovl: Filter invalid inodes with missing lookup function

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=175acd44580000

kernel config: https://syzkaller.appspot.com/x/.config?x=f63d146f1af4415a
dashboard link: https://syzkaller.appspot.com/bug?extid=9db6b2a6346d266bd206

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.