Re: [syzbot] [nilfs2?] general protection fault in nilfs_btree_insert

[Ryusuke Konishi]

On Wed, Dec 28, 2022 at 10:40 PM syzbot wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    51094a24b85e Merge tag 'hardening-v6.2-rc1-fixes' of git:/..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=172e2b44480000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4e2d7bfa2d6d5a76
> dashboard link: https://syzkaller.appspot.com/bug?extid=ede796cecd5296353515
> compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1243578c480000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1506f1ac480000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/a26f3769fdfb/disk-51094a24.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/5decc3ae71d7/vmlinux-51094a24.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/dd2ac18a5b04/bzImage-51094a24.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/559169c47ec8/mount_0.gz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+ede796cecd5296353515@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> loop0: detected capacity change from 0 to 2048
> general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
> CPU: 1 PID: 5066 Comm: syz-executor153 Not tainted 6.1.0-syzkaller-14587-g51094a24b85e #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
> RIP: 0010:nilfs_btree_get_nonroot_node fs/nilfs2/btree.c:418 [inline]
> RIP: 0010:nilfs_btree_prepare_insert fs/nilfs2/btree.c:1077 [inline]
> RIP: 0010:nilfs_btree_insert+0x6d3/0x1c10 fs/nilfs2/btree.c:1238
> Code: bc 24 80 00 00 00 4c 89 f8 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 ff e8 4b 02 92 fe 4d 8b 3f 49 83 c7 28 4c 89 f8 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 ff e8 2e 02 92 fe 4d 8b 3f 49 83 c7 02
> RSP: 0018:ffffc90003bcf4a0 EFLAGS: 00010206
> RAX: 0000000000000005 RBX: 0000000000000001 RCX: 0000000000000000
> RDX: ffff88807eba3a80 RSI: 0000000000000002 RDI: 0000000000000001
> RBP: ffffc90003bcf630 R08: ffffffff834f80d8 R09: ffffed100571ff9b
> R10: ffffed100571ff9b R11: 1ffff1100571ff9a R12: ffff888021d03480
> R13: dffffc0000000000 R14: 0000000000000002 R15: 0000000000000028
> FS:  000055555588c300(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f4614ff5a70 CR3: 000000007eb7c000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  nilfs_bmap_do_insert fs/nilfs2/bmap.c:121 [inline]
>  nilfs_bmap_insert+0x20d/0x360 fs/nilfs2/bmap.c:147
>  nilfs_get_block+0x414/0x8d0 fs/nilfs2/inode.c:101
>  __block_write_begin_int+0x54c/0x1a80 fs/buffer.c:1991
>  __block_write_begin fs/buffer.c:2041 [inline]
>  block_write_begin+0x93/0x1e0 fs/buffer.c:2102
>  nilfs_write_begin+0x9c/0x110 fs/nilfs2/inode.c:261
>  generic_perform_write+0x2e4/0x5e0 mm/filemap.c:3772
>  __generic_file_write_iter+0x176/0x400 mm/filemap.c:3900
>  generic_file_write_iter+0xab/0x310 mm/filemap.c:3932
>  call_write_iter include/linux/fs.h:2186 [inline]
>  new_sync_write fs/read_write.c:491 [inline]
>  vfs_write+0x7dc/0xc50 fs/read_write.c:584
>  ksys_write+0x177/0x2a0 fs/read_write.c:637
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7fca03d80b59
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 14 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 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffdd1df8c28 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fca03d80b59
> RDX: 000000000000002f RSI: 0000000020000040 RDI: 0000000000000004
> RBP: 00007fca03d40160 R08: 0000000000000014 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007fca03d401f0
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:nilfs_btree_get_nonroot_node fs/nilfs2/btree.c:418 [inline]
> RIP: 0010:nilfs_btree_prepare_insert fs/nilfs2/btree.c:1077 [inline]
> RIP: 0010:nilfs_btree_insert+0x6d3/0x1c10 fs/nilfs2/btree.c:1238
> Code: bc 24 80 00 00 00 4c 89 f8 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 ff e8 4b 02 92 fe 4d 8b 3f 49 83 c7 28 4c 89 f8 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 ff e8 2e 02 92 fe 4d 8b 3f 49 83 c7 02
> RSP: 0018:ffffc90003bcf4a0 EFLAGS: 00010206
> RAX: 0000000000000005 RBX: 0000000000000001 RCX: 0000000000000000
> RDX: ffff88807eba3a80 RSI: 0000000000000002 RDI: 0000000000000001
> RBP: ffffc90003bcf630 R08: ffffffff834f80d8 R09: ffffed100571ff9b
> R10: ffffed100571ff9b R11: 1ffff1100571ff9a R12: ffff888021d03480
> R13: dffffc0000000000 R14: 0000000000000002 R15: 0000000000000028
> FS:  000055555588c300(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055a236e64fe0 CR3: 000000007eb7c000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
>    0:   bc 24 80 00 00          mov    $0x8024,%esp
>    5:   00 4c 89 f8             add    %cl,-0x8(%rcx,%rcx,4)
>    9:   48 c1 e8 03             shr    $0x3,%rax
>    d:   42 80 3c 28 00          cmpb   $0x0,(%rax,%r13,1)
>   12:   74 08                   je     0x1c
>   14:   4c 89 ff                mov    %r15,%rdi
>   17:   e8 4b 02 92 fe          callq  0xfe920267
>   1c:   4d 8b 3f                mov    (%r15),%r15
>   1f:   49 83 c7 28             add    $0x28,%r15
>   23:   4c 89 f8                mov    %r15,%rax
>   26:   48 c1 e8 03             shr    $0x3,%rax
> * 2a:   42 80 3c 28 00          cmpb   $0x0,(%rax,%r13,1) <-- trapping instruction
>   2f:   74 08                   je     0x39
>   31:   4c 89 ff                mov    %r15,%rdi
>   34:   e8 2e 02 92 fe          callq  0xfe920267
>   39:   4d 8b 3f                mov    (%r15),%r15
>   3c:   49 83 c7 02             add    $0x2,%r15
>
>
> ---
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>
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This seems to be an unfixed bug in nilfs2.

As a result of analysis using the C-reproducer, it turns out that
nilfs_btree_insert() may cause the above oops when nilfs2 reads a
corrupted disk image and a b-tree node block address translation fails
due to a DAT metadata corruption.

It's necessary to correct the error handling in the above case.  I'll
take a closer look to fix this.

Ryusuke Konishi