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

[Li Feng]

Marc-André Lureau <address@hidden> 于2020年5月8日周五 下午8:32写道：
>
> 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.
Yes. However, the issue did exist in the master code base.
The test case in patch 2 revealed this issue.

>
> >
> > 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().
Yes, in the test case I try to inject an error in char_socket_ping_pong.
Any concerns about these two patches?
>
> --
> Marc-André Lureau