On Mon, Mar 15, 2021 at 1:13 PM Philippe Mathieu-Daudé <phi...@redhat.com>
wrote:
> Hi Mahmoud,
>
> On 3/15/21 11:58 AM, Mahmoud Mandour wrote:
> > Replaced a call to malloc() and its respective call to free()
> > with g_malloc() and g_free().
> >
> > g_malloc() is preferred more than g_try_* functions, which
> > return NULL on error, when the size of the requested
> > allocation is small. This is because allocating few
> > bytes should not be a problem in a healthy system.
> > Otherwise, the system is already in a critical state.
> >
> > Subsequently, removed NULL-checking after g_malloc().
> >
> > Signed-off-by: Mahmoud Mandour <ma.mando...@gmail.com>
> > ---
> > util/compatfd.c | 8 ++------
> > 1 file changed, 2 insertions(+), 6 deletions(-)
> >
> > diff --git a/util/compatfd.c b/util/compatfd.c
> > index 174f394533..a8ec525c6c 100644
> > --- a/util/compatfd.c
> > +++ b/util/compatfd.c
> > @@ -72,14 +72,10 @@ static int qemu_signalfd_compat(const sigset_t *mask)
> > QemuThread thread;
> > int fds[2];
> >
> > - info = malloc(sizeof(*info));
> > - if (info == NULL) {
> > - errno = ENOMEM;
> > - return -1;
> > - }
> > + info = g_malloc(sizeof(*info));
>
> Watch out...
>
> https://developer.gnome.org/glib/stable/glib-Memory-Allocation.html
>
> If any call to allocate memory using functions g_new(), g_new0(),
> g_renew(), g_malloc(), g_malloc0(), g_malloc0_n(), g_realloc(),
> and g_realloc_n() fails, the application is terminated.
>
> So with your change instead of handling ENOMEM the QEMU process is
> simply killed.
>
> Don't you want to use g_try_new(struct sigfd_compat_info, 1) here
> instead?
>
> >
> > if (pipe(fds) == -1) {
> > - free(info);
> > + g_free(info);
> > return -1;
> > }
> >
> >
>
>
Hello Mr. Philippe,
That's originally what I did and I sent a patch that uses a g_try_*
variant, and was
instructed by Mr. Thomas Huth that it was better to use g_malloc instead
because this is a small allocation and the process is better killed if such
an allocation fails because the system is already in a very critical state
if it does not handle a small allocation well.
You can find Mr. Thomas reply to my previous patch here:
Re: [PATCH 5/8] util/compatfd.c: Replaced a malloc with GLib's variant
(gnu.org)
<https://lists.gnu.org/archive/html/qemu-devel/2021-03/msg05067.html>
You can instruct me on what to do further.
Thanks
Mahmoud
