[Android 5.10] BUG: unable to handle kernel NULL pointer dereference in __lookup_slow

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e253c52bbdfc Merge 5.10.247 into android13-5.10-lts
git tree: android13-5.10-lts
console output: https://syzkaller.appspot.com/x/log.txt?x=1686369a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=5193c33e6e6dcf8b
dashboard link: https://syzkaller.appspot.com/bug?extid=e88f99e7392dbd54eb96
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=111e0074580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17a68f92580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1f48e3a38826/disk-e253c52b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/17f909517783/vmlinux-e253c52b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1fc1230e0a59/bzImage-e253c52b.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/83b64c28fed4/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=13dbe69a580000)
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/08281815fc3c/mount_4.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=13a68f92580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e88f99...@syzkaller.appspotmail.com

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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 10ff93067 P4D 10ff93067 PUD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 379 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc900022c7a18 EFLAGS: 00010246
RAX: 1ffffffff0a1ad10 RBX: 1ffff1102126a710 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff888109353880 RDI: ffff8881209ac4f0
RBP: ffffc900022c7af0 R08: dffffc0000000000 R09: fffffbfff0d9a1f1
R10: fffffbfff0d9a1f1 R11: 1ffffffff0d9a1f0 R12: dffffc0000000000
R13: ffff888109353880 R14: ffffffff850d6880 R15: 1ffff92000458f48
FS: 000055557ae18500(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000010ffa1000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__lookup_slow+0x2aa/0x3e0 fs/namei.c:1648
lookup_one_len+0x18e/0x2c0 fs/namei.c:2664
incfs_lookup_dentry+0x60/0xb0 fs/incfs/data_mgmt.c:210
ioctl_create_file fs/incfs/pseudo_files.c:555 [inline]
pending_reads_dispatch_ioctl+0x1555/0x1d40 fs/incfs/pseudo_files.c:1028
vfs_ioctl fs/ioctl.c:48 [inline]
__do_sys_ioctl fs/ioctl.c:753 [inline]
__se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:739
__x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:739
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f2b78bdd749
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:00007ffd00f32ad8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f2b78e33fa0 RCX: 00007f2b78bdd749
RDX: 00002000000000c0 RSI: 00000000c058671e RDI: 0000000000000005
RBP: 00007f2b78c61f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2b78e33fa0 R14: 00007f2b78e33fa0 R15: 0000000000000003
Modules linked in:
CR2: 0000000000000000
---[ end trace e8bc856044036ce9 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc900022c7a18 EFLAGS: 00010246
RAX: 1ffffffff0a1ad10 RBX: 1ffff1102126a710 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff888109353880 RDI: ffff8881209ac4f0
RBP: ffffc900022c7af0 R08: dffffc0000000000 R09: fffffbfff0d9a1f1
R10: fffffbfff0d9a1f1 R11: 1ffffffff0d9a1f0 R12: dffffc0000000000
R13: ffff888109353880 R14: ffffffff850d6880 R15: 1ffff92000458f48
FS: 000055557ae18500(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000010ffa1000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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