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

Allen, John posted 1 patch 6 days ago
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git fetch https://github.com/patchew-project/libvirt tags/patchew/20190415144245.26992-1-john.allen@amd.com

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

Posted by Allen, John 6 days ago
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@amd.com>
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++) {

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