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

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; --- 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); + /* htole64 is not provided by gnulib, so we do the conversion by hand */ l = bitmap->map; for (i = j = 0; i < len; i++, j++) {