Re: [PATCH v3 1/2] io/channel: fix crash when qio_channel_readv_all return 0

[Marc-André Lureau]

Hi

On Fri, May 8, 2020 at 7:14 AM Li Feng <address@hidden> wrote:
>
> Root cause:
> From `man recvmsg`, the RETURN VALUE says:
> These  calls return the number of bytes received, or -1 if an error occurred.
> In the event of an error, errno is set to indicate the error.
> The return value will be 0 when the peer has performed an orderly shutdown.
>
> When an error happens, the socket will be closed, and recvmsg return 0,
> then error_setg will trigger a crash.
>
> This unit test could reproduce this issue:
> tests/test-char -p /char/socket/client/reconnect-error/unix

Current master doesn't trigger the backtrace, it's only after your patch 2.

>
> The core file backtrace is :
>
> (gdb) bt
>     #0  0x00007ffff5ac3277 in raise () from /lib64/libc.so.6
>     #1  0x00007ffff5ac4968 in abort () from /lib64/libc.so.6
>     #2  0x00005555555aaa94 in error_handle_fatal (errp=<optimized out>, 
> err=0x7fffec0012d0) at util/error.c:40
>     #3  0x00005555555aab6d in error_setv (errp=0x555555802a08 <error_abort>, 
> src=0x5555555c4280 "io/channel.c", line=148,
>         func=0x5555555c4580 <__func__.17489> "qio_channel_readv_all", 
> err_class=ERROR_CLASS_GENERIC_ERROR,
>         fmt=<optimized out>, ap=0x7ffff423bae0, suffix=0x0) at util/error.c:73
>     #4  0x00005555555aacf0 in error_setg_internal 
> (errp=errp@entry=0x555555802a08 <error_abort>,
>         src=src@entry=0x5555555c4280 "io/channel.c", line=line@entry=148,
>         func=func@entry=0x5555555c4580 <__func__.17489> 
> "qio_channel_readv_all",
>         fmt=fmt@entry=0x5555555c43a0 "Unexpected end-of-file before all bytes 
> were read") at util/error.c:97
>     #5  0x000055555556c25c in qio_channel_readv_all (ioc=<optimized out>, 
> iov=<optimized out>, niov=<optimized out>,
>         errp=0x555555802a08 <error_abort>) at io/channel.c:147
>     #6  0x000055555556c29a in qio_channel_read_all (ioc=<optimized out>, 
> buf=<optimized out>, buflen=<optimized out>,
>         errp=<optimized out>) at io/channel.c:247
>     #7  0x000055555556ad22 in char_socket_ping_pong (ioc=0x7fffec0008c0) at 
> tests/test-char.c:732
>     #8  0x000055555556ae12 in char_socket_client_server_thread 
> (data=data@entry=0x55555582e350) at tests/test-char.c:891
>     #9  0x00005555555a95b6 in qemu_thread_start (args=<optimized out>) at 
> util/qemu-thread-posix.c:519
>     #10 0x00007ffff5e61e25 in start_thread () from /lib64/libpthread.so.0
>     #11 0x00007ffff5b8bbad in clone () from /lib64/libc.so.6
>
> Signed-off-by: Li Feng <address@hidden>
> ---
>  io/channel.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/io/channel.c b/io/channel.c
> index e4376eb0bc..1a4a505f01 100644
> --- a/io/channel.c
> +++ b/io/channel.c
> @@ -144,8 +144,6 @@ int qio_channel_readv_all(QIOChannel *ioc,
>
>      if (ret == 0) {
>          ret = -1;
> -        error_setg(errp,
> -                   "Unexpected end-of-file before all bytes were read");

Nack, this code is fine.

The problem is that the test case doesn't expect a disconnect in
char_socket_ping_pong().

-- 
Marc-André Lureau