Re: [Qemu-devel] [Qemu-block] [PATCH 1/1] block/sheepdog: fix argument passed to qemu_strtoul()

[Jeff Cody <jcody@redhat.com>]

On Wed, Mar 02, 2016 at 04:27:31PM +0100, Max Reitz wrote:
> On 02.03.2016 16:16, Jeff Cody wrote:
> > The function qemu_strtoul() reads 'unsigned long' sized data,
> > which is larger than uint32_t on 64-bit machines.
> > 
> > Even though the snap_id field in the header is 32-bits, we must
> > accomodate the full size in qemu_strtoul().
> > 
> > Reported-by: Paolo Bonzini <pbonzini@redhat.com>
> > Signed-off-by: Jeff Cody <jcody@redhat.com>
> > ---
> >  block/sheepdog.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/block/sheepdog.c b/block/sheepdog.c
> > index 8739acc..c6bf900 100644
> > --- a/block/sheepdog.c
> > +++ b/block/sheepdog.c
> > @@ -2543,7 +2543,7 @@ static int sd_snapshot_delete(BlockDriverState *bs,
> >                                const char *name,
> >                                Error **errp)
> >  {
> > -    uint32_t snap_id = 0;
> > +    unsigned long snap_id = 0;
> >      char snap_tag[SD_MAX_VDI_TAG_LEN];
> >      Error *local_err = NULL;
> >      int fd, ret;
> > @@ -2565,12 +2565,12 @@ static int sd_snapshot_delete(BlockDriverState *bs,
> >      memset(buf, 0, sizeof(buf));
> >      memset(snap_tag, 0, sizeof(snap_tag));
> >      pstrcpy(buf, SD_MAX_VDI_LEN, s->name);
> > -    if (qemu_strtoul(snapshot_id, NULL, 10, (unsigned long *)&snap_id)) {
> > +    if (qemu_strtoul(snapshot_id, NULL, 10, &snap_id)) {
> >          return -1;
> >      }
> >  
> >      if (snap_id) {
> > -        hdr.snapid = snap_id;
> > +        hdr.snapid = (uint32_t) snap_id;
> 
> Maybe we should do an overflow check before?
>

Probably not a bad idea - easy enough, and that would prevent a false
positive match due to id truncation.  I'll spin a v2.

Jeff