Re: [libvirt] [PATCH] Handle copying bitmaps to larger data buffers

On Mon, Apr 15, 2019 at 02:43:07PM +0000, Allen, John wrote: > If a bitmap of a shorter length than the data buffer is passed to > virBitmapToDataBuf, it will read off the end of the bitmap and copy junk > into the returned buffer. Add a check to only copy the length of the > bitmap to the buffer. > > The problem can be observed after setting a vcpu affinity using the vcpupin > command on a system with a large number of cores: > # virsh vcpupin example_domain 0 0 > # virsh vcpupin example_domain 0 > VCPU CPU Affinity > --------------------------- > 0 0,192,197-198,202 > > Signed-off-by: John Allen <john.allen(a)amd.com&gt; > --- Thanks for the patch, pushed now. > diff --git a/src/util/virbitmap.c b/src/util/virbitmap.c > index d074f29e54..021174cbb3 100644 > --- a/src/util/virbitmap.c > +++ b/src/util/virbitmap.c > @@ -824,11 +824,15 @@ virBitmapToDataBuf(virBitmapPtr bitmap, > unsigned char *bytes, > size_t len) > { > + size_t nbytes = bitmap->map_len * (VIR_BITMAP_BITS_PER_UNIT / CHAR_BIT); > unsigned long *l; > size_t i, j; > > memset(bytes, 0, len); > > + /* If bitmap and buffer differ in size, only fill to the smaller length */ > + len = MIN(len, nbytes); > + I would probably store the min back to nbytes and used that but it doesn't matter. > /* htole64 is not provided by gnulib, so we do the conversion by hand */ > l = bitmap->map; > for (i = j = 0; i < len; i++, j++) {