[syzbot] [autofs?] general protection fault in autofs_fill_super

[syzbot] [autofs?] general protection fault in autofs_fill_super

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    4bbdb725a36b Merge tag 'iommu-updates-v6.7' of git://git.k..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=15dc14a8e80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=beb32a598fd79db9
dashboard link: https://syzkaller.appspot.com/bug?extid=662f87a8ef490f45fa64
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14384a7b680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fd459eb1acfc/disk-4bbdb725.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d784829734e1/vmlinux-4bbdb725.xz
kernel image: https://storage.googleapis.com/syzbot-assets/db2c9e9ae9c3/bzImage-4bbdb725.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+662f87a8ef490f45fa64@syzkaller.appspotmail.com

Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe4723a6f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fae5d99bf80 RCX: 00007fae5d87cae9
RDX: 0000000020000040 RSI: 0000000020000380 RDI: 0000000000000000
RBP: 00007ffe4723a750 R08: 0000000020000400 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00000000000009f9 R14: 00007fae5d99bf80 R15: 00007fae5d99bf80
 </TASK>
general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 PID: 5098 Comm: syz-executor.0 Not tainted 6.6.0-syzkaller-15601-g4bbdb725a36b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
RIP: 0010:autofs_fill_super+0x47d/0xb50 fs/autofs/inode.c:334
Code: 03 60 d7 9f 8b 4d 8d 67 04 48 8b 14 24 48 89 d0 48 c1 e8 03 42 0f b6 04 30 84 c0 0f 85 58 03 00 00 8b 1a 4c 89 e0 48 c1 e8 03 <42> 0f b6 04 30 84 c0 4c 89 f5 0f 85 61 03 00 00 41 89 5f 04 4d 8d
RSP: 0018:ffffc90003bafc90 EFLAGS: 00010247
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88807b190000
RDX: ffff8880136beac0 RSI: ffffffff8bbdc620 RDI: ffffffff8bbdc5e0
RBP: ffff8880206d0580 R08: ffffffff8da2aa13 R09: 1ffffffff1b45542
R10: dffffc0000000000 R11: fffffbfff1b45543 R12: 0000000000000004
R13: ffff8880206d0500 R14: dffffc0000000000 R15: 0000000000000000
FS:  0000555555cbc480(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe47239e08 CR3: 0000000024f32000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 vfs_get_super fs/super.c:1338 [inline]
 get_tree_nodev+0xb4/0x140 fs/super.c:1357
 vfs_get_tree+0x8c/0x280 fs/super.c:1771
 do_new_mount+0x28f/0xae0 fs/namespace.c:3337
 do_mount fs/namespace.c:3677 [inline]
 __do_sys_mount fs/namespace.c:3886 [inline]
 __se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3863
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7fae5d87cae9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe4723a6f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fae5d99bf80 RCX: 00007fae5d87cae9
RDX: 0000000020000040 RSI: 0000000020000380 RDI: 0000000000000000
RBP: 00007ffe4723a750 R08: 0000000020000400 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00000000000009f9 R14: 00007fae5d99bf80 R15: 00007fae5d99bf80
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:autofs_fill_super+0x47d/0xb50 fs/autofs/inode.c:334
Code: 03 60 d7 9f 8b 4d 8d 67 04 48 8b 14 24 48 89 d0 48 c1 e8 03 42 0f b6 04 30 84 c0 0f 85 58 03 00 00 8b 1a 4c 89 e0 48 c1 e8 03 <42> 0f b6 04 30 84 c0 4c 89 f5 0f 85 61 03 00 00 41 89 5f 04 4d 8d
RSP: 0018:ffffc90003bafc90 EFLAGS: 00010247
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88807b190000
RDX: ffff8880136beac0 RSI: ffffffff8bbdc620 RDI: ffffffff8bbdc5e0
RBP: ffff8880206d0580 R08: ffffffff8da2aa13 R09: 1ffffffff1b45542
R10: dffffc0000000000 R11: fffffbfff1b45543 R12: 0000000000000004
R13: ffff8880206d0500 R14: dffffc0000000000 R15: 0000000000000000
FS:  0000555555cbc480(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe47239e08 CR3: 0000000024f32000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	28 00                	sub    %al,(%rax)
   2:	00 00                	add    %al,(%rax)
   4:	75 05                	jne    0xb
   6:	48 83 c4 28          	add    $0x28,%rsp
   a:	c3                   	ret
   b:	e8 e1 20 00 00       	call   0x20f1
  10:	90                   	nop
  11:	48 89 f8             	mov    %rdi,%rax
  14:	48 89 f7             	mov    %rsi,%rdi
  17:	48 89 d6             	mov    %rdx,%rsi
  1a:	48 89 ca             	mov    %rcx,%rdx
  1d:	4d 89 c2             	mov    %r8,%r10
  20:	4d 89 c8             	mov    %r9,%r8
  23:	4c 8b 4c 24 08       	mov    0x8(%rsp),%r9
  28:	0f 05                	syscall
* 2a:	48 3d 01 f0 ff ff    	cmp    $0xfffffffffffff001,%rax <-- trapping instruction
  30:	73 01                	jae    0x33
  32:	c3                   	ret
  33:	48 c7 c1 b0 ff ff ff 	mov    $0xffffffffffffffb0,%rcx
  3a:	f7 d8                	neg    %eax
  3c:	64 89 01             	mov    %eax,%fs:(%rcx)
  3f:	48                   	rex.W


---
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Re: [syzbot] [autofs?] general protection fault in autofs_fill_super

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+662f87a8ef490f45fa64@syzkaller.appspotmail.com

Tested on:

commit:         4bbdb725 Merge tag 'iommu-updates-v6.7' of git://git.k..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=17a6c75b680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=beb32a598fd79db9
dashboard link: https://syzkaller.appspot.com/bug?extid=662f87a8ef490f45fa64
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=17bb3be0e80000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [autofs?] general protection fault in autofs_fill_super

[syzbot]

syzbot has bisected this issue to:

commit e6ec453bd0f03a60a80f00f95ae2eaa260faa3c2
Author: Ian Kent <raven@themaw.net>
Date:   Fri Sep 22 04:12:14 2023 +0000

    autofs: convert autofs to use the new mount api

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12d04220e80000
start commit:   4bbdb725a36b Merge tag 'iommu-updates-v6.7' of git://git.k..
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=11d04220e80000
console output: https://syzkaller.appspot.com/x/log.txt?x=16d04220e80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=beb32a598fd79db9
dashboard link: https://syzkaller.appspot.com/bug?extid=662f87a8ef490f45fa64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14384a7b680000

Reported-by: syzbot+662f87a8ef490f45fa64@syzkaller.appspotmail.com
Fixes: e6ec453bd0f0 ("autofs: convert autofs to use the new mount api")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection