Re: [syzbot] KASAN: use-after-free Read in btrfs_scan_one_device (2)

[syzbot <syzbot+82650a4e0ed38f218363@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
general protection fault in btrfs_iget

general protection fault, probably for non-canonical address 0xdffffc000000003e: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000001f0-0x00000000000001f7]
CPU: 0 PID: 3975 Comm: syz-executor324 Not tainted 5.17.0-rc5-syzkaller-00306-g2293be58d6a1-dirty #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
RIP: 0010:btrfs_inode_hash fs/btrfs/btrfs_inode.h:258 [inline]
RIP: 0010:btrfs_iget_locked fs/btrfs/inode.c:5503 [inline]
RIP: 0010:btrfs_iget_path fs/btrfs/inode.c:5525 [inline]
RIP: 0010:btrfs_iget+0x7a/0x210 fs/btrfs/inode.c:5554
Code: f3 65 48 8b 04 25 28 00 00 00 48 89 44 24 58 31 c0 e8 3a 5f 33 fe 49 8d be f7 01 00 00 48 89 f8 48 89 fe 48 c1 e8 03 83 e6 07 <42> 0f b6 14 20 49 8d 86 fe 01 00 00 48 89 c1 48 c1 e9 03 42 0f b6
RSP: 0018:ffffc900029ef940 EFLAGS: 00010202

RAX: 000000000000003e RBX: 1ffff9200053df28 RCX: 0000000000000000
RDX: ffff88801c40e2c0 RSI: 0000000000000007 RDI: 00000000000001f7
RBP: ffff888023dce000 R08: 0000000000000000 R09: ffffc900029ef6f7
R10: ffffffff8912a851 R11: 0000000000000001 R12: dffffc0000000000
R13: 0000000000000100 R14: 0000000000000000 R15: 0000000000000000
FS:  00007fec6fcc0700(0000) GS:ffff88802ca00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000563567f04618 CR3: 0000000026c41000 CR4: 0000000000150ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 btrfs_fill_super fs/btrfs/super.c:1364 [inline]
 btrfs_mount_root.cold+0x93/0x1a2 fs/btrfs/super.c:1726
 legacy_get_tree+0x105/0x220 fs/fs_context.c:610
 vfs_get_tree+0x89/0x2f0 fs/super.c:1497
 fc_mount fs/namespace.c:1030 [inline]
 vfs_kern_mount.part.0+0xd3/0x170 fs/namespace.c:1060
 vfs_kern_mount+0x3c/0x60 fs/namespace.c:1047
 btrfs_mount+0x234/0xa60 fs/btrfs/super.c:1788
 legacy_get_tree+0x105/0x220 fs/fs_context.c:610
 vfs_get_tree+0x89/0x2f0 fs/super.c:1497
 do_new_mount fs/namespace.c:3024 [inline]
 path_mount+0x1320/0x1fa0 fs/namespace.c:3354
 do_mount fs/namespace.c:3367 [inline]
 __do_sys_mount fs/namespace.c:3575 [inline]
 __se_sys_mount fs/namespace.c:3552 [inline]
 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3552
 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+0x44/0xae
RIP: 0033:0x7fec6fd142a9
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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fec6fcc02f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fec6fd993e0 RCX: 00007fec6fd142a9
RDX: 0000000020000140 RSI: 0000000020000100 RDI: 0000000020000080
RBP: 0030656c69662f2e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000246 R12: 00007fec6fd65478
R13: 00007fec6fd651f0 R14: 00007fec6fd650a8 R15: 00007fec6fd993e8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:btrfs_inode_hash fs/btrfs/btrfs_inode.h:258 [inline]
RIP: 0010:btrfs_iget_locked fs/btrfs/inode.c:5503 [inline]
RIP: 0010:btrfs_iget_path fs/btrfs/inode.c:5525 [inline]
RIP: 0010:btrfs_iget+0x7a/0x210 fs/btrfs/inode.c:5554
Code: f3 65 48 8b 04 25 28 00 00 00 48 89 44 24 58 31 c0 e8 3a 5f 33 fe 49 8d be f7 01 00 00 48 89 f8 48 89 fe 48 c1 e8 03 83 e6 07 <42> 0f b6 14 20 49 8d 86 fe 01 00 00 48 89 c1 48 c1 e9 03 42 0f b6
RSP: 0018:ffffc900029ef940 EFLAGS: 00010202
RAX: 000000000000003e RBX: 1ffff9200053df28 RCX: 0000000000000000
RDX: ffff88801c40e2c0 RSI: 0000000000000007 RDI: 00000000000001f7
RBP: ffff888023dce000 R08: 0000000000000000 R09: ffffc900029ef6f7
R10: ffffffff8912a851 R11: 0000000000000001 R12: dffffc0000000000
R13: 0000000000000100 R14: 0000000000000000 R15: 0000000000000000
FS:  00007fec6fcc0700(0000) GS:ffff88802ca00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000563567f04618 CR3: 0000000026c41000 CR4: 0000000000150ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	f3 65 48 8b 04 25 28 	repz mov %gs:0x28,%rax
   7:	00 00 00
   a:	48 89 44 24 58       	mov    %rax,0x58(%rsp)
   f:	31 c0                	xor    %eax,%eax
  11:	e8 3a 5f 33 fe       	callq  0xfe335f50
  16:	49 8d be f7 01 00 00 	lea    0x1f7(%r14),%rdi
  1d:	48 89 f8             	mov    %rdi,%rax
  20:	48 89 fe             	mov    %rdi,%rsi
  23:	48 c1 e8 03          	shr    $0x3,%rax
  27:	83 e6 07             	and    $0x7,%esi
* 2a:	42 0f b6 14 20       	movzbl (%rax,%r12,1),%edx <-- trapping instruction
  2f:	49 8d 86 fe 01 00 00 	lea    0x1fe(%r14),%rax
  36:	48 89 c1             	mov    %rax,%rcx
  39:	48 c1 e9 03          	shr    $0x3,%rcx
  3d:	42                   	rex.X
  3e:	0f                   	.byte 0xf
  3f:	b6                   	.byte 0xb6


Tested on:

commit:         2293be58 Merge tag 'trace-v5.17-rc4' of git://git.kern..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
console output: https://syzkaller.appspot.com/x/log.txt?x=112736d6700000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5f28851401b410e5
dashboard link: https://syzkaller.appspot.com/bug?extid=82650a4e0ed38f218363
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=11de2ad6700000