[syzbot] [erofs?] general protection fault in erofs_bread (2)

Thu May 18 03:35:39 AEST 2023

Hello,

syzbot found the following issue on:

HEAD commit:    f1fcbaa18b28 Linux 6.4-rc2
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=114aa029280000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6beb6ffe4f59ef2a
dashboard link: https://syzkaller.appspot.com/bug?extid=bbb353775d51424087f2
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=13dd834e280000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=167ef106280000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4adf207e9d5e/disk-f1fcbaa1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9e7cce92f611/vmlinux-f1fcbaa1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cfd911b80f89/bzImage-f1fcbaa1.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/a2583fbaaf14/mount_2.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bbb353775d51424087f2 at syzkaller.appspotmail.com

erofs: (device loop0): EXPERIMENTAL global deduplication feature in use. Use at your own risk!
general protection fault, probably for non-canonical address 0xdffffc0000000019: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000000c8-0x00000000000000cf]
CPU: 0 PID: 4995 Comm: syz-executor235 Not tainted 6.4.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023
RIP: 0010:erofs_bread+0x56/0x6d0 fs/erofs/data.c:38
Code: 48 c1 ea 03 80 3c 02 00 0f 85 15 06 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 23 49 8d bc 24 ca 00 00 00 48 89 fa 48 c1 ea 03 <0f> b6 04 02 48 89 fa 83 e2 07 38 d0 7f 08 84 c0 0f 85 82 05 00 00
RSP: 0018:ffffc900034b7980 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffffc900034b7af8 RCX: 0000000000000000
RDX: 0000000000000019 RSI: ffffffff83c1ea5f RDI: 00000000000000ca
RBP: 0000000000000000 R08: 0000000000000001 R09: 000000000000003f
R10: 000000000000000c R11: ffffffff81d50f12 R12: 0000000000000000
R13: 0000000000000001 R14: ffff888019bd4000 R15: ffff888019bd4000
FS:  0000555555bf6300(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc664ae0ca0 CR3: 0000000020cc6000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 erofs_read_metadata+0xbb/0x490 fs/erofs/super.c:137
 erofs_xattr_prefixes_init+0x3b1/0x590 fs/erofs/xattr.c:684
 erofs_fc_fill_super+0x1734/0x2a80 fs/erofs/super.c:825
 get_tree_bdev+0x44a/0x770 fs/super.c:1303
 vfs_get_tree+0x8d/0x350 fs/super.c:1510
 do_new_mount fs/namespace.c:3039 [inline]
 path_mount+0x134b/0x1e40 fs/namespace.c:3369
 do_mount fs/namespace.c:3382 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount fs/namespace.c:3568 [inline]
 __x64_sys_mount+0x283/0x300 fs/namespace.c:3568
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fc664b09e5a
Code: 83 c4 08 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 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:00007ffd1310be98 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007fc664b09e5a
RDX: 0000000020000180 RSI: 0000000020000140 RDI: 00007ffd1310bea0
RBP: 00007ffd1310bea0 R08: 00007ffd1310bee0 R09: 00000000000001d4
R10: 0000000001000801 R11: 0000000000000286 R12: 0000000000000005
R13: 0000555555bf62c0 R14: 00007ffd1310bee0 R15: 0000000000000000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:erofs_bread+0x56/0x6d0 fs/erofs/data.c:38
Code: 48 c1 ea 03 80 3c 02 00 0f 85 15 06 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 23 49 8d bc 24 ca 00 00 00 48 89 fa 48 c1 ea 03 <0f> b6 04 02 48 89 fa 83 e2 07 38 d0 7f 08 84 c0 0f 85 82 05 00 00
RSP: 0018:ffffc900034b7980 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffffc900034b7af8 RCX: 0000000000000000
RDX: 0000000000000019 RSI: ffffffff83c1ea5f RDI: 00000000000000ca
RBP: 0000000000000000 R08: 0000000000000001 R09: 000000000000003f
R10: 000000000000000c R11: ffffffff81d50f12 R12: 0000000000000000
R13: 0000000000000001 R14: ffff888019bd4000 R15: ffff888019bd4000
FS:  0000555555bf6300(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb0e8fdab10 CR3: 0000000020cc6000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
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 15 06 00 00    	jne    0x623
   e:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  15:	fc ff df
  18:	4c 8b 23             	mov    (%rbx),%r12
  1b:	49 8d bc 24 ca 00 00 	lea    0xca(%r12),%rdi
  22:	00
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	0f b6 04 02          	movzbl (%rdx,%rax,1),%eax <-- trapping instruction
  2e:	48 89 fa             	mov    %rdi,%rdx
  31:	83 e2 07             	and    $0x7,%edx
  34:	38 d0                	cmp    %dl,%al
  36:	7f 08                	jg     0x40
  38:	84 c0                	test   %al,%al
  3a:	0f 85 82 05 00 00    	jne    0x5c2

---
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 at googlegroups.com.

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

If the bug is already fixed, 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 change bug's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

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

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