Re: [PATCH-for-5.0] qga-posix: Avoid crashing process when failing to allocate memory

[Philippe Mathieu-Daudé]

On 3/25/20 7:19 AM, Dietmar Maurer wrote:
> but error_setg() also calls malloc, so this does not help at all?

IIUC the problem, you can send a QMP command to ask to read let's say 
3GB of a file, and QEMU crashes. But this doesn't mean there the .heap 
is empty, there is probably few bytes still available, enough to respond 
with an error message.

> > On March 24, 2020 8:48 PM Philippe Mathieu-Daudé <address@hidden> wrote:
> >
> >   
> > Similarly to commit 807e2b6fce0 for Windows, kindly return a
> > QMP error message instead of crashing the whole process.
> >
> > Cc: address@hidden
> > Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1594054
> > Reported-by: Fakhri Zulkifli <address@hidden>
> > Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> > ---
> >   qga/commands-posix.c | 8 +++++++-
> >   1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> > index 93474ff770..8f127788e6 100644
> > --- a/qga/commands-posix.c
> > +++ b/qga/commands-posix.c
> > @@ -493,7 +493,13 @@ struct GuestFileRead *qmp_guest_file_read(int64_t handle, 
> > bool has_count,
> >           gfh->state = RW_STATE_NEW;
> >       }
> >   
> > -    buf = g_malloc0(count+1);
> > +    buf = g_try_malloc0(count + 1);
> > +    if (!buf) {
> > +        error_setg(errp,
> > +                   "failed to allocate sufficient memory "
> > +                   "to complete the requested service");
> > +        return NULL;
> > +    }
> >       read_count = fread(buf, 1, count, fh);
> >       if (ferror(fh)) {
> >           error_setg_errno(errp, errno, "failed to read file");
> > --
> > 2.21.1