Re: [syzbot] WARNING in _copy_from_iter

[Eric Dumazet]

On Thu, Dec 8, 2022 at 8:36 PM syzbot
<syzbot+d43608d061e8847ec9f3@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    591cd61541b9 Add linux-next specific files for 20221207
> git tree:       linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=15d12929880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=8b2d3e63e054c24f
> dashboard link: https://syzkaller.appspot.com/bug?extid=d43608d061e8847ec9f3
> 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=172536fb880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12d00a7d880000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/bc862c01ec56/disk-591cd615.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/8f9b93f8ed2f/vmlinux-591cd615.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/9d5cb636d548/bzImage-591cd615.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d43608d061e8847ec9f3@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 5086 at lib/iov_iter.c:629 _copy_from_iter+0x2ed/0xf70 lib/iov_iter.c:629
> Modules linked in:
> CPU: 0 PID: 5086 Comm: syz-executor371 Not tainted 6.1.0-rc8-next-20221207-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
> RIP: 0010:_copy_from_iter+0x2ed/0xf70 lib/iov_iter.c:629
> Code: 77 fd 44 89 fb e9 33 ff ff ff e8 be 34 77 fd be 79 02 00 00 48 c7 c7 e0 59 a6 8a e8 fd 6f b0 fd e9 17 fe ff ff e8 a3 34 77 fd <0f> 0b 45 31 ff e9 7b ff ff ff e8 94 34 77 fd 31 ff 89 ee e8 fb 30
> RSP: 0018:ffffc90003e1f828 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: ffff888026548000 RSI: ffffffff840a6e5d RDI: 0000000000000001
> RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: ffffc90003e1fd00
> R13: ffff888079c498f8 R14: ffffc90003e1fd00 R15: 0000000000000000
> FS:  0000555557073300(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000045b630 CR3: 000000007d92a000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  copy_from_iter include/linux/uio.h:187 [inline]
>  copy_from_iter_full include/linux/uio.h:194 [inline]
>  tipc_msg_build+0x2d4/0x10a0 net/tipc/msg.c:404
>  __tipc_sendmsg+0xada/0x1870 net/tipc/socket.c:1505
>  tipc_connect+0x57b/0x6b0 net/tipc/socket.c:2624
>  __sys_connect_file+0x153/0x1a0 net/socket.c:1976
>  __sys_connect+0x165/0x1a0 net/socket.c:1993
>  __do_sys_connect net/socket.c:2003 [inline]
>  __se_sys_connect net/socket.c:2000 [inline]
>  __x64_sys_connect+0x73/0xb0 net/socket.c:2000
>  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: 0033:0x7fac68eeeb19
> 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:00007ffe4214d778 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fac68eeeb19
> RDX: 0000000000000010 RSI: 0000000020000000 RDI: 0000000000000003
> RBP: 00007fac68eb2cc0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007fac68eb2d50
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>  </TASK>
>
>
> ---
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>
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Exposes an old bug in tipc ?

Seems a new check added by Al in :

Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date:   Thu Sep 15 20:11:15 2022 -0400

    iov_iter: saner checks for attempt to copy to/from iterator

    instead of "don't do it to ITER_PIPE" check for ->data_source being
    false on copying from iterator.  Check for !->data_source for
    copying to iterator, while we are at it.

    Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>