linux-kernel - [syzbot] [fs?] general protection fault in mntput

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-ID: <6928c5c3.a70a0220.d98e3.011a.GAE@google.com>
Date: Thu, 27 Nov 2025 13:42:27 -0800
From: syzbot <syzbot+94048264da5715c251f9@...kaller.appspotmail.com>
To: brauner@...nel.org, jack@...e.cz, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, 
	viro@...iv.linux.org.uk
Subject: [syzbot] [fs?] general protection fault in mntput

Hello,

syzbot found the following issue on:

HEAD commit:    92fd6e84175b Add linux-next specific files for 20251125
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13a55612580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bf77a4e0e3514deb
dashboard link: https://syzkaller.appspot.com/bug?extid=94048264da5715c251f9
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=1215f612580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17082f42580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bee2604d495b/disk-92fd6e84.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b12aade49e2c/vmlinux-92fd6e84.xz
kernel image: https://storage.googleapis.com/syzbot-assets/286fd34158cb/bzImage-92fd6e84.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+94048264da5715c251f9@...kaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000023: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000118-0x000000000000011f]
CPU: 0 UID: 0 PID: 6414 Comm: syz.3.69 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:mntput+0x31/0xc0 fs/namespace.c:1430
Code: 41 56 41 54 53 48 89 fb e8 1c da 7e ff 48 85 db 74 47 49 bf 00 00 00 00 00 fc ff df 4c 8d b3 24 01 00 00 4d 89 f4 49 c1 ec 03 <43> 0f b6 04 3c 84 c0 75 50 48 83 c3 e0 41 8b 2e 31 ff 89 ee e8 26
RSP: 0018:ffffc9000462fd90 EFLAGS: 00010202
RAX: ffffffff8242c664 RBX: fffffffffffffff4 RCX: ffff888077aa5b80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: fffffffffffffff4
RBP: ffffc9000462fed0 R08: ffff888077aa5b87 R09: 1ffff1100ef54b70
R10: dffffc0000000000 R11: ffffed100ef54b71 R12: 0000000000000023
R13: dffffc0000000000 R14: 0000000000000118 R15: dffffc0000000000
FS:  00007fdf2c77f6c0(0000) GS:ffff888125e8b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555575df7808 CR3: 0000000076002000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __do_sys_fsmount fs/namespace.c:4380 [inline]
 __se_sys_fsmount+0x893/0xa90 fs/namespace.c:4279
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdf2b98f749
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:00007fdf2c77f038 EFLAGS: 00000246 ORIG_RAX: 00000000000001b0
RAX: ffffffffffffffda RBX: 00007fdf2bbe6180 RCX: 00007fdf2b98f749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007fdf2ba13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdf2bbe6218 R14: 00007fdf2bbe6180 R15: 00007ffd8048bbc8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:mntput+0x31/0xc0 fs/namespace.c:1430
Code: 41 56 41 54 53 48 89 fb e8 1c da 7e ff 48 85 db 74 47 49 bf 00 00 00 00 00 fc ff df 4c 8d b3 24 01 00 00 4d 89 f4 49 c1 ec 03 <43> 0f b6 04 3c 84 c0 75 50 48 83 c3 e0 41 8b 2e 31 ff 89 ee e8 26
RSP: 0018:ffffc9000462fd90 EFLAGS: 00010202
RAX: ffffffff8242c664 RBX: fffffffffffffff4 RCX: ffff888077aa5b80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: fffffffffffffff4
RBP: ffffc9000462fed0 R08: ffff888077aa5b87 R09: 1ffff1100ef54b70
R10: dffffc0000000000 R11: ffffed100ef54b71 R12: 0000000000000023
R13: dffffc0000000000 R14: 0000000000000118 R15: dffffc0000000000
FS:  00007fdf2c77f6c0(0000) GS:ffff888125f8b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd4a51d5e8 CR3: 0000000076002000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	41 56                	push   %r14
   2:	41 54                	push   %r12
   4:	53                   	push   %rbx
   5:	48 89 fb             	mov    %rdi,%rbx
   8:	e8 1c da 7e ff       	call   0xff7eda29
   d:	48 85 db             	test   %rbx,%rbx
  10:	74 47                	je     0x59
  12:	49 bf 00 00 00 00 00 	movabs $0xdffffc0000000000,%r15
  19:	fc ff df
  1c:	4c 8d b3 24 01 00 00 	lea    0x124(%rbx),%r14
  23:	4d 89 f4             	mov    %r14,%r12
  26:	49 c1 ec 03          	shr    $0x3,%r12
* 2a:	43 0f b6 04 3c       	movzbl (%r12,%r15,1),%eax <-- trapping instruction
  2f:	84 c0                	test   %al,%al
  31:	75 50                	jne    0x83
  33:	48 83 c3 e0          	add    $0xffffffffffffffe0,%rbx
  37:	41 8b 2e             	mov    (%r14),%ebp
  3a:	31 ff                	xor    %edi,%edi
  3c:	89 ee                	mov    %ebp,%esi
  3e:	e8                   	.byte 0xe8
  3f:	26                   	es


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@...glegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup