Re: [Qemu-devel] [PATCH for-2.3 3/6] vmdk: Clean up descriptor file reading

[Fam Zheng]

On Tue, 12/02 12:10, Don Koch wrote:
> On Tue, 2 Dec 2014 15:39:14 +0800
> Fam Zheng <address@hidden> wrote:
> 
> > Zeroing a buffer that will be filled right after is not necessary, and
> > allocating a power of two + 1 is naughty.
> > 
> > Suggested-by: Markus Armbruster <address@hidden>
> > Signed-off-by: Fam Zheng <address@hidden>
> > ---
> >  block/vmdk.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/block/vmdk.c b/block/vmdk.c
> > index 28d22db..0c5769c 100644
> > --- a/block/vmdk.c
> > +++ b/block/vmdk.c
> > @@ -558,14 +558,15 @@ static char *vmdk_read_desc(BlockDriverState *file, 
> > uint64_t desc_offset,
> >      }
> >  
> >      size = MIN(size, 1 << 20);  /* avoid unbounded allocation */
> > -    buf = g_malloc0(size + 1);
> > +    buf = g_malloc(size);
> 
> For a file that is less than 1<<20 bytes, won't this throw away the last byte?
> Maybe better is:
>     size = MIN(size, (1 << 20) - 1);
>     buf = g_malloc(size + 1);
> Leave the bdrv_pread as it was and...
> 
> >  
> > -    ret = bdrv_pread(file, desc_offset, buf, size);
> > +    ret = bdrv_pread(file, desc_offset, buf, size - 1);
> >      if (ret < 0) {
> >          error_setg_errno(errp, -ret, "Could not read from file");
> >          g_free(buf);
> >          return NULL;
> >      }
> > +    buf[ret - 1] = 0;
> 
> ...zero the last byte changes to:
>     buf[ret] = 0;

Yes. I'll respin this one. Thanks.

Fam

> 
> >  
> >      return buf;
> >  }
> > -- 
> > 1.9.3
> 
> -d