Re: [PATCH v3 2/8] gdbstub: Try unlinking the unix socket before binding

[Ilya Leoshkevich]

On Wed, 2025-01-08 at 16:10 +0000, Alex Bennée wrote:
> Ilya Leoshkevich <iii@linux.ibm.com> writes:
> 
> > In case an emulated process execve()s another emulated process,
> > bind()
> > will fail, because the socket already exists. So try deleting it.
> > 
> > Note that it is not possible to handle this in do_execv(): deleting
> > gdbserver_user_state.socket_path before safe_execve() is not
> > correct,
> > because the latter may fail, and afterwards we may lose control.
> > 
> > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> > ---
> >  gdbstub/user.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/gdbstub/user.c b/gdbstub/user.c
> > index ef52f249ce9..c900d0a52fe 100644
> > --- a/gdbstub/user.c
> > +++ b/gdbstub/user.c
> > @@ -337,6 +337,7 @@ static int gdbserver_open_socket(const char
> > *path)
> >  
> >      sockaddr.sun_family = AF_UNIX;
> >      pstrcpy(sockaddr.sun_path, sizeof(sockaddr.sun_path) - 1,
> > path);
> > +    unlink(sockaddr.sun_path);
> 
> Should we be checking for errors here? What do we expect when
> attempting
> to unlink a non-existent path? -EIO?

ENOENT I guess.
I will add a check that requires either success or ENOENT.

> >      ret = bind(fd, (struct sockaddr *)&sockaddr,
> > sizeof(sockaddr));
> >      if (ret < 0) {
> >          perror("bind socket");