[Android 5.15] general protection fault in mnt_want_write

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 05eea940894a ANDROID: GKI: preserve the kernel API for str..
git tree: android13-5.15-lts
console output: https://syzkaller.appspot.com/x/log.txt?x=14702d6a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=daefb08bb2811735
dashboard link: https://syzkaller.appspot.com/bug?extid=a1bd788fbebb8124ade5
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=11399fba580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13b7cca6580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e158e2d934a2/disk-05eea940.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/95d8715fb0e7/vmlinux-05eea940.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d046a12b451d/bzImage-05eea940.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a1bd78...@syzkaller.appspotmail.com

incfs: Can't find or create .incomplete dir in ./file0
incfs: mount failed -22
incfs: ino conflict with backing FS 2
general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 1 PID: 375 Comm: syz.2.18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:mnt_want_write+0x2f/0x2e0 fs/namespace.c:386
Code: 57 41 56 41 55 41 54 53 50 48 89 fb 49 bf 00 00 00 00 00 fc ff df e8 d0 88 b1 ff 48 89 5d d0 4c 8d 73 08 4c 89 f3 48 c1 eb 03 <42> 80 3c 3b 00 74 08 4c 89 f7 e8 a2 be f0 ff 4d 8b 3e 4d 8d a7 a8
RSP: 0018:ffffc90000b87a70 EFLAGS: 00010202
RAX: ffffffff81b851b0 RBX: 0000000000000001 RCX: ffff888110092780
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000b87aa0 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000170f2a R12: ffffc90000b87d40
R13: ffff88810d166660 R14: 0000000000000008 R15: dffffc0000000000
FS: 000055557140d500(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555571430948 CR3: 0000000110297000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
ovl_want_write+0x92/0xa0 fs/overlayfs/util.c:22
ovl_setattr+0x51/0x460 fs/overlayfs/inode.c:32
notify_change+0xbca/0xe90 fs/attr.c:505
incfs_setattr+0x260/0x3e0 fs/incfs/vfs.c:1680
notify_change+0xbca/0xe90 fs/attr.c:505
chmod_common+0x223/0x3c0 fs/open.c:583
do_fchmodat+0xd4/0x1a0 fs/open.c:622
__do_sys_chmod fs/open.c:640 [inline]
__se_sys_chmod fs/open.c:638 [inline]
__x64_sys_chmod+0x60/0x70 fs/open.c:638
x64_sys_call+0xad/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:91
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: 0033:0x7fa093da6e59
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:00007ffc874f3278 EFLAGS: 00000246 ORIG_RAX: 000000000000005a
RAX: ffffffffffffffda RBX: 00007fa09401ffa0 RCX: 00007fa093da6e59
RDX: 0000000000000000 RSI: 0000000000000054 RDI: 0000200000000000
RBP: 00007fa093e3cd6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa09401ffac R14: 00007fa09401ffa0 R15: 00007fa09401ffa0
</TASK>
Modules linked in:
---[ end trace 8ddb333560664b77 ]---
RIP: 0010:mnt_want_write+0x2f/0x2e0 fs/namespace.c:386
Code: 57 41 56 41 55 41 54 53 50 48 89 fb 49 bf 00 00 00 00 00 fc ff df e8 d0 88 b1 ff 48 89 5d d0 4c 8d 73 08 4c 89 f3 48 c1 eb 03 <42> 80 3c 3b 00 74 08 4c 89 f7 e8 a2 be f0 ff 4d 8b 3e 4d 8d a7 a8
RSP: 0018:ffffc90000b87a70 EFLAGS: 00010202
RAX: ffffffff81b851b0 RBX: 0000000000000001 RCX: ffff888110092780
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000b87aa0 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000170f2a R12: ffffc90000b87d40
R13: ffff88810d166660 R14: 0000000000000008 R15: dffffc0000000000
FS: 000055557140d500(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000001000 CR3: 0000000110297000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 57 push %rdi
1: 41 56 push %r14
3: 41 55 push %r13
5: 41 54 push %r12
7: 53 push %rbx
8: 50 push %rax
9: 48 89 fb mov %rdi,%rbx
c: 49 bf 00 00 00 00 00 movabs $0xdffffc0000000000,%r15
13: fc ff df
16: e8 d0 88 b1 ff call 0xffb188eb
1b: 48 89 5d d0 mov %rbx,-0x30(%rbp)
1f: 4c 8d 73 08 lea 0x8(%rbx),%r14
23: 4c 89 f3 mov %r14,%rbx
26: 48 c1 eb 03 shr $0x3,%rbx
* 2a: 42 80 3c 3b 00 cmpb $0x0,(%rbx,%r15,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 4c 89 f7 mov %r14,%rdi
34: e8 a2 be f0 ff call 0xfff0bedb
39: 4d 8b 3e mov (%r14),%r15
3c: 4d rex.WRB
3d: 8d .byte 0x8d
3e: a7 cmpsl %es:(%rdi),%ds:(%rsi)
3f: a8 .byte 0xa8


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