[syzbot] WARNING in ovl_fh_to_dentry

[syzbot] WARNING in ovl_fh_to_dentry

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    483fed3b5dc8 Add linux-next specific files for 20220921
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13b13f30880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=849cb9f70f15b1ba
dashboard link: https://syzkaller.appspot.com/bug?extid=9d14351a171d0d1c7955
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=14283ac4880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=156da4ef080000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1cb3f4618323/disk-483fed3b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cc02cb30b495/vmlinux-483fed3b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9d14351a171d0d1c7955@syzkaller.appspotmail.com

------------[ cut here ]------------
memcpy: detected field-spanning write (size 93) of single field "&fh->fb" at fs/overlayfs/export.c:799 (size 21)
WARNING: CPU: 0 PID: 3608 at fs/overlayfs/export.c:799 ovl_fid_to_fh fs/overlayfs/export.c:799 [inline]
WARNING: CPU: 0 PID: 3608 at fs/overlayfs/export.c:799 ovl_fh_to_dentry+0x880/0x950 fs/overlayfs/export.c:812
Modules linked in:
CPU: 1 PID: 3608 Comm: syz-executor365 Not tainted 6.0.0-rc6-next-20220921-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2022
RIP: 0010:ovl_fid_to_fh fs/overlayfs/export.c:799 [inline]
RIP: 0010:ovl_fh_to_dentry+0x880/0x950 fs/overlayfs/export.c:812
Code: f9 ff ff e8 62 b6 ab fe b9 15 00 00 00 4c 89 f6 48 c7 c2 a0 0f 28 8a 48 c7 c7 00 10 28 8a c6 05 a7 86 fa 0a 01 e8 4d ad 76 06 <0f> 0b e9 ec f8 ff ff 49 c7 c6 ea ff ff ff bb ea ff ff ff c7 44 24
RSP: 0018:ffffc90003d7fb30 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000060 RCX: 0000000000000000
RDX: ffff88801f9f8000 RSI: ffffffff81620348 RDI: fffff520007aff58
RBP: ffff88801798b900 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000000 R11: 203a7970636d656d R12: 00000000000000fb
R13: 1ffff920007aff6e R14: 000000000000005d R15: ffff88801798b903
FS:  0000555555748300(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2ec877aa70 CR3: 0000000021a2b000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 exportfs_decode_fh_raw+0x127/0x7d0 fs/exportfs/expfs.c:435
 exportfs_decode_fh+0x38/0x90 fs/exportfs/expfs.c:575
 do_handle_to_path fs/fhandle.c:152 [inline]
 handle_to_path fs/fhandle.c:207 [inline]
 do_handle_open+0x2b6/0x8b0 fs/fhandle.c:223
 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: 0033:0x7fa84bf85cc9
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 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:00007ffd45ccfbd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000130
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fa84bf85cc9
RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 00007fa84bf49e70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000073 R11: 0000000000000246 R12: 00007fa84bf49f00
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>


---
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Re: [syzbot] WARNING in ovl_fh_to_dentry

[Kees Cook]

On Fri, Sep 23, 2022 at 09:05:40AM -0700, syzbot wrote:
> syzbot found the following issue on:
> 
> HEAD commit:    483fed3b5dc8 Add linux-next specific files for 20220921
> git tree:       linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=13b13f30880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=849cb9f70f15b1ba
> dashboard link: https://syzkaller.appspot.com/bug?extid=9d14351a171d0d1c7955
> 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=14283ac4880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=156da4ef080000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/1cb3f4618323/disk-483fed3b.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/cc02cb30b495/vmlinux-483fed3b.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+9d14351a171d0d1c7955@syzkaller.appspotmail.com
> 
> ------------[ cut here ]------------
> memcpy: detected field-spanning write (size 93) of single field "&fh->fb" at fs/overlayfs/export.c:799 (size 21)

I've send a patch for this now:
https://lore.kernel.org/linux-hardening/20220924073315.3593031-1-keescook@chromium.org

-- 
Kees Cook