[Android 5.15] general protection fault in __is_local_mountpoint

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dc151d2e3144 Revert "batman-adv: stop tp_meter sessions du..
git tree: android13-5.15-lts
console output: https://syzkaller.appspot.com/x/log.txt?x=11107789580000
kernel config: https://syzkaller.appspot.com/x/.config?x=43676e801f1929a9
dashboard link: https://syzkaller.appspot.com/bug?extid=8fc31d8f0ff9600238a1
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14dc8ab9580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11ae6746580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d3a56ba2b6dd/disk-dc151d2e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8b6846da446f/vmlinux-dc151d2e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1628ef9bb65b/bzImage-dc151d2e.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/27b0e5b93bd2/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=16ae6746580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8fc31d...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
CPU: 0 PID: 412 Comm: syz.4.21 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
RIP: 0010:__is_local_mountpoint+0x56/0x1a0 fs/namespace.c:706
Code: 49 81 c6 30 08 00 00 4c 89 f0 48 c1 e8 03 80 3c 18 00 74 08 4c 89 f7 e8 b8 aa f0 ff 4d 8b 36 49 83 c6 18 4c 89 f0 48 c1 e8 03 <80> 3c 18 00 74 08 4c 89 f7 e8 9c aa f0 ff 4d 8b 3e 48 c7 c7 20 80
RSP: 0018:ffffc90000c77868 EFLAGS: 00010206
RAX: 0000000000000003 RBX: dffffc0000000000 RCX: ffff8881150d0000
RDX: 0000000000000000 RSI: 0000000000010000 RDI: ffff888111c83660
RBP: ffffc90000c778a0 R08: ffff88812127b0c7 R09: 1ffff1102424f618
R10: dffffc0000000000 R11: ffffed102424f619 R12: 1ffff11024240e10
R13: 0000000000010000 R14: 0000000000000018 R15: 1ffff110223906cc
FS: 0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055556e66a908 CR3: 000000011b882000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
is_local_mountpoint fs/mount.h:142 [inline]
vfs_rmdir+0x12d/0x450 fs/namei.c:4150
incfs_kill_sb+0xfe/0x210 fs/incfs/vfs.c:1989
deactivate_locked_super+0xa0/0x100 fs/super.c:335
deactivate_super+0xaf/0xe0 fs/super.c:366
cleanup_mnt+0x44f/0x500 fs/namespace.c:1149
__cleanup_mnt+0x19/0x20 fs/namespace.c:1156
task_work_run+0x127/0x190 kernel/task_work.c:188
exit_task_work include/linux/task_work.h:33 [inline]
do_exit+0xb70/0x29a0 kernel/exit.c:890
do_group_exit+0x149/0x310 kernel/exit.c:1004
get_signal+0x64f/0x1430 kernel/signal.c:2908
arch_do_signal_or_restart+0xe2/0x1100 arch/x86/kernel/signal.c:867
handle_signal_work kernel/entry/common.c:154 [inline]
exit_to_user_mode_loop+0xa7/0xe0 kernel/entry/common.c:178
exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f02343ece99
Code: Unable to access opcode bytes at RIP 0x7f02343ece6f.
RSP: 002b:00007f023424e0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f0234674fa8 RCX: 00007f02343ece99
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f0234674fa8
RBP: 00007f0234674fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0234675038 R14: 00007ffe8087c8a0 R15: 00007ffe8087c988
</TASK>
Modules linked in:
---[ end trace 0744723d67335ae4 ]---
RIP: 0010:__is_local_mountpoint+0x56/0x1a0 fs/namespace.c:706
Code: 49 81 c6 30 08 00 00 4c 89 f0 48 c1 e8 03 80 3c 18 00 74 08 4c 89 f7 e8 b8 aa f0 ff 4d 8b 36 49 83 c6 18 4c 89 f0 48 c1 e8 03 <80> 3c 18 00 74 08 4c 89 f7 e8 9c aa f0 ff 4d 8b 3e 48 c7 c7 20 80
RSP: 0018:ffffc90000c77868 EFLAGS: 00010206
RAX: 0000000000000003 RBX: dffffc0000000000 RCX: ffff8881150d0000
RDX: 0000000000000000 RSI: 0000000000010000 RDI: ffff888111c83660
RBP: ffffc90000c778a0 R08: ffff88812127b0c7 R09: 1ffff1102424f618
R10: dffffc0000000000 R11: ffffed102424f619 R12: 1ffff11024240e10
R13: 0000000000010000 R14: 0000000000000018 R15: 1ffff110223906cc
FS: 0000000000000000(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f05dd923000 CR3: 000000012dbdc000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 49 81 c6 30 08 00 00 add $0x830,%r14
7: 4c 89 f0 mov %r14,%rax
a: 48 c1 e8 03 shr $0x3,%rax
e: 80 3c 18 00 cmpb $0x0,(%rax,%rbx,1)
12: 74 08 je 0x1c
14: 4c 89 f7 mov %r14,%rdi
17: e8 b8 aa f0 ff call 0xfff0aad4
1c: 4d 8b 36 mov (%r14),%r14
1f: 49 83 c6 18 add $0x18,%r14
23: 4c 89 f0 mov %r14,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 80 3c 18 00 cmpb $0x0,(%rax,%rbx,1) <-- trapping instruction
2e: 74 08 je 0x38
30: 4c 89 f7 mov %r14,%rdi
33: e8 9c aa f0 ff call 0xfff0aad4
38: 4d 8b 3e mov (%r14),%r15
3b: 48 rex.W
3c: c7 .byte 0xc7
3d: c7 (bad)
3e: 20 .byte 0x20
3f: 80 .byte 0x80


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