[syzbot] [udf?] general protection fault in d_splice_alias

[syzbot <syzbot+a9c0867e4d1dd0c7ab19@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    69e858e0b8b2 Merge tag 'uml-for-linus-6.14-rc1' of git://g..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=11bfc518580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d1a6d4df5fcc342f
dashboard link: https://syzkaller.appspot.com/bug?extid=a9c0867e4d1dd0c7ab19
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=125d0eb0580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13a595f8580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a4b4612f419c/disk-69e858e0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/07abf7c78a98/vmlinux-69e858e0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/085b44906cce/bzImage-69e858e0.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/0e8d208f30b1/mount_0.gz

The issue was bisected to:

commit 30d61efe118cad1a73ad2ad66a3298e4abdf9f41
Author: Al Viro <viro@zeniv.linux.org.uk>
Date:   Mon Jan 6 02:33:17 2025 +0000

    9p: fix ->rename_sem exclusion

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1050fddf980000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1250fddf980000
console output: https://syzkaller.appspot.com/x/log.txt?x=1450fddf980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a9c0867e4d1dd0c7ab19@syzkaller.appspotmail.com
Fixes: 30d61efe118c ("9p: fix ->rename_sem exclusion")

UDF-fs: INFO Mounting volume 'LinuxUDF', timestamp 2022/11/22 14:59 (1000)
Oops: general protection fault, probably for non-canonical address 0xdffffc000000000d: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
CPU: 0 UID: 0 PID: 5832 Comm: syz-executor165 Not tainted 6.13.0-syzkaller-09760-g69e858e0b8b2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
RIP: 0010:__d_unalias fs/dcache.c:2969 [inline]
RIP: 0010:d_splice_alias+0x9cd/0xf30 fs/dcache.c:3037
Code: 48 c1 ea 03 80 3c 02 00 0f 85 4e 05 00 00 49 8b 85 70 ff ff ff 48 ba 00 00 00 00 00 fc ff df 48 8d 78 68 48 89 f9 48 c1 e9 03 <80> 3c 11 00 0f 85 14 05 00 00 48 8b 40 68 48 85 c0 74 31 48 89 44
RSP: 0018:ffffc90003667c18 EFLAGS: 00010212
RAX: 0000000000000000 RBX: ffff88807dbd7318 RCX: 000000000000000d
RDX: dffffc0000000000 RSI: ffffffff82348f0c RDI: 0000000000000068
RBP: ffff8880754107b8 R08: 0000000000000000 R09: ffffed100f23d67a
R10: ffff8880791eb3d3 R11: 0000000000000032 R12: ffff8880791eb318
R13: ffff8880791eafd8 R14: ffff8880791eaeb0 R15: ffff8880791eaf48
FS:  0000555581642380(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe875be000 CR3: 0000000076b7a000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 udf_lookup+0x191/0x240 fs/udf/namei.c:130
 lookup_one_qstr_excl+0x120/0x190 fs/namei.c:1693
 do_rmdir+0x247/0x410 fs/namei.c:4444
 __do_sys_rmdir fs/namei.c:4474 [inline]
 __se_sys_rmdir fs/namei.c:4472 [inline]
 __x64_sys_rmdir+0xc5/0x110 fs/namei.c:4472
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9ee0142d99
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 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:00007ffe875bd248 EFLAGS: 00000246 ORIG_RAX: 0000000000000054
RAX: ffffffffffffffda RBX: 6f72746e6f632f2e RCX: 00007f9ee0142d99
RDX: 00007f9ee0142d99 RSI: 00007f9ee0142d99 RDI: 0000000020000100
RBP: 00007f9ee01b75f0 R08: 00005555816434c0 R09: 00005555816434c0
R10: 00005555816434c0 R11: 0000000000000246 R12: 00007ffe875bd270
R13: 00007ffe875bd498 R14: 431bde82d7b634db R15: 00007f9ee018c03b
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__d_unalias fs/dcache.c:2969 [inline]
RIP: 0010:d_splice_alias+0x9cd/0xf30 fs/dcache.c:3037
Code: 48 c1 ea 03 80 3c 02 00 0f 85 4e 05 00 00 49 8b 85 70 ff ff ff 48 ba 00 00 00 00 00 fc ff df 48 8d 78 68 48 89 f9 48 c1 e9 03 <80> 3c 11 00 0f 85 14 05 00 00 48 8b 40 68 48 85 c0 74 31 48 89 44
RSP: 0018:ffffc90003667c18 EFLAGS: 00010212
RAX: 0000000000000000 RBX: ffff88807dbd7318 RCX: 000000000000000d
RDX: dffffc0000000000 RSI: ffffffff82348f0c RDI: 0000000000000068
RBP: ffff8880754107b8 R08: 0000000000000000 R09: ffffed100f23d67a
R10: ffff8880791eb3d3 R11: 0000000000000032 R12: ffff8880791eb318
R13: ffff8880791eafd8 R14: ffff8880791eaeb0 R15: ffff8880791eaf48
FS:  0000555581642380(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe875be000 CR3: 0000000076b7a000 CR4: 0000000000350ef0
----------------
Code disassembly (best guess):
   0:	48 c1 ea 03          	shr    $0x3,%rdx
   4:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
   8:	0f 85 4e 05 00 00    	jne    0x55c
   e:	49 8b 85 70 ff ff ff 	mov    -0x90(%r13),%rax
  15:	48 ba 00 00 00 00 00 	movabs $0xdffffc0000000000,%rdx
  1c:	fc ff df
  1f:	48 8d 78 68          	lea    0x68(%rax),%rdi
  23:	48 89 f9             	mov    %rdi,%rcx
  26:	48 c1 e9 03          	shr    $0x3,%rcx
* 2a:	80 3c 11 00          	cmpb   $0x0,(%rcx,%rdx,1) <-- trapping instruction
  2e:	0f 85 14 05 00 00    	jne    0x548
  34:	48 8b 40 68          	mov    0x68(%rax),%rax
  38:	48 85 c0             	test   %rax,%rax
  3b:	74 31                	je     0x6e
  3d:	48                   	rex.W
  3e:	89                   	.byte 0x89
  3f:	44                   	rex.R


---
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