[syzbot] general protection fault in hugetlbfs_parse_param

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a72b55bc981b Add linux-next specific files for 20221019
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=14510b06880000
kernel config: https://syzkaller.appspot.com/x/.config?x=200524babbc01b2a
dashboard link: https://syzkaller.appspot.com/bug?extid=a3e6acd85ded5c16a709
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15bbe2d2880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16678bd6880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fa24fb5893fd/disk-a72b55bc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cf1b7e7b579c/vmlinux-a72b55bc.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a3e6ac...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 PID: 3607 Comm: syz-executor454 Not tainted 6.1.0-rc1-next-20221019-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
RIP: 0010:hugetlbfs_parse_param+0x1dd/0x8e0 fs/hugetlbfs/inode.c:1380
Code: 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 84 06 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b 65 10 4c 89 e2 48 c1 ea 03 <0f> b6 04 02 4c 89 e2 83 e2 07 38 d0 7f 0c 84 c0 74 08 4c 89 e7 e8
RSP: 0018:ffffc90003a5fb48 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 1ffff9200074bf6b RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff82350899 RDI: ffffc90003a5fc78
RBP: ffff88801db5ac00 R08: 0000000000000005 R09: 0000000000000006
R10: 0000000000000005 R11: 000000000008c001 R12: 0000000000000000
R13: ffffc90003a5fc68 R14: ffff88801d5fbf00 R15: ffff88801db5acd0
FS: 00005555569383c0(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020001000 CR3: 0000000074e4c000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
vfs_parse_fs_param fs/fs_context.c:148 [inline]
vfs_parse_fs_param+0x1f9/0x3c0 fs/fs_context.c:129
vfs_parse_fs_string+0xdb/0x170 fs/fs_context.c:191
generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:231
do_new_mount fs/namespace.c:3036 [inline]
path_mount+0x12de/0x1e20 fs/namespace.c:3370
do_mount fs/namespace.c:3383 [inline]
__do_sys_mount fs/namespace.c:3591 [inline]
__se_sys_mount fs/namespace.c:3568 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f06d8633fe9
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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe278e8e18 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffe278e8e28 RCX: 00007f06d8633fe9
RDX: 0000000020000040 RSI: 0000000020000000 RDI: 0000000000000000
RBP: 00007ffe278e8e20 R08: 0000000020000280 R09: 00007f06d85f20a0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:hugetlbfs_parse_param+0x1dd/0x8e0 fs/hugetlbfs/inode.c:1380
Code: 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 84 06 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b 65 10 4c 89 e2 48 c1 ea 03 <0f> b6 04 02 4c 89 e2 83 e2 07 38 d0 7f 0c 84 c0 74 08 4c 89 e7 e8
RSP: 0018:ffffc90003a5fb48 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 1ffff9200074bf6b RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff82350899 RDI: ffffc90003a5fc78
RBP: ffff88801db5ac00 R08: 0000000000000005 R09: 0000000000000006
R10: 0000000000000005 R11: 000000000008c001 R12: 0000000000000000
R13: ffffc90003a5fc68 R14: ffff88801d5fbf00 R15: ffff88801db5acd0
FS: 00005555569383c0(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f06d86453c0 CR3: 0000000074e4c000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 3 bytes skipped:
0: df 48 89 fisttps -0x77(%rax)
3: fa cli
4: 48 c1 ea 03 shr $0x3,%rdx
8: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
c: 0f 85 84 06 00 00 jne 0x696
12: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
19: fc ff df
1c: 4d 8b 65 10 mov 0x10(%r13),%r12
20: 4c 89 e2 mov %r12,%rdx
23: 48 c1 ea 03 shr $0x3,%rdx
* 27: 0f b6 04 02 movzbl (%rdx,%rax,1),%eax <-- trapping instruction
2b: 4c 89 e2 mov %r12,%rdx
2e: 83 e2 07 and $0x7,%edx
31: 38 d0 cmp %dl,%al
33: 7f 0c jg 0x41
35: 84 c0 test %al,%al
37: 74 08 je 0x41
39: 4c 89 e7 mov %r12,%rdi
3c: e8 .byte 0xe8


---
This report is generated by a bot. It may contain errors.
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syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+a3e6ac...@syzkaller.appspotmail.com

Tested on:

commit: acee3e83 Add linux-next specific files for 20221020
git tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1586ad3c880000
kernel config: https://syzkaller.appspot.com/x/.config?x=c82245cfb913f766

dashboard link: https://syzkaller.appspot.com/bug?extid=a3e6acd85ded5c16a709
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=113107d6880000

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

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+a3e6ac...@syzkaller.appspotmail.com

Tested on:

commit: acee3e83 Add linux-next specific files for 20221020
git tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next.git master

console output: https://syzkaller.appspot.com/x/log.txt?x=12b089d2880000

kernel config: https://syzkaller.appspot.com/x/.config?x=c82245cfb913f766
dashboard link: https://syzkaller.appspot.com/bug?extid=a3e6acd85ded5c16a709
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=175641d2880000