[Android 5.15] BUG: unable to handle kernel NULL pointer dereference in __lookup_slow

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7fad219d720d Merge android13-5.15 into android13-5.15-lts
git tree: android13-5.15-lts
console output: https://syzkaller.appspot.com/x/log.txt?x=10b96f16580000
kernel config: https://syzkaller.appspot.com/x/.config?x=daefb08bb2811735
dashboard link: https://syzkaller.appspot.com/bug?extid=b335889a8d156d1cad3f
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17ef82d2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17d4ba6a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7e1209a70d88/disk-7fad219d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9313bf35ee22/vmlinux-7fad219d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6e63a5a4613d/bzImage-7fad219d.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/7d052f60d5f6/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=13ef82d2580000)
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/f369a9f9abec/mount_4.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=15a3a4ce580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b33588...@syzkaller.appspotmail.com

WARNING: The mand mount option has been deprecated and
and is ignored by this kernel. Remove the mand
option from the mount to silence this warning.
=======================================================
exFAT-fs (loop2): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
exFAT-fs (loop2): Medium has reported failures. Some data may be lost.
exFAT-fs (loop2): failed to load upcase table (idx : 0x00010000, chksum : 0xe2e35dda, 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 12db61067 P4D 12db61067 PUD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 357 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc90000b779d8 EFLAGS: 00010246
RAX: 1ffffffff0aa0cd8 RBX: 1ffff1102137cf10 RCX: ffff8881103be2c0
RDX: 0000000000000000 RSI: ffff888109be7880 RDI: ffff888121372350
RBP: ffffc90000b77ab0 R08: ffffffff8711f5b7 R09: 1ffffffff0e23eb6
R10: dffffc0000000000 R11: fffffbfff0e23eb7 R12: dffffc0000000000
R13: ffff888109be7880 R14: ffffffff855066c0 R15: 1ffff9200016ef40
FS: 0000555563cec500(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000012db51000 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+0x161e/0x1e70 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: 0033:0x7ff9942a0819
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:00007fff2a4e9918 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff994519fa0 RCX: 00007ff9942a0819
RDX: 00002000000000c0 RSI: 00000000c058671e RDI: 0000000000000005
RBP: 00007ff994336c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff994519fac R14: 00007ff994519fa0 R15: 00007ff994519fa0
</TASK>
Modules linked in:
CR2: 0000000000000000
---[ end trace f62f978b3530e73e ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc90000b779d8 EFLAGS: 00010246
RAX: 1ffffffff0aa0cd8 RBX: 1ffff1102137cf10 RCX: ffff8881103be2c0
RDX: 0000000000000000 RSI: ffff888109be7880 RDI: ffff888121372350
RBP: ffffc90000b77ab0 R08: ffffffff8711f5b7 R09: 1ffffffff0e23eb6
R10: dffffc0000000000 R11: fffffbfff0e23eb7 R12: dffffc0000000000
R13: ffff888109be7880 R14: ffffffff855066c0 R15: 1ffff9200016ef40
FS: 0000555563cec500(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000012db51000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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