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virBitmapShrink: Do not attempt to clear bits beyond end of buffer

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'virBitmapShrink' clears the bits beyond the end of the bitmap when
shrinking and then reallocates to match the new size. As it uses the
address of the first bit beyond the bitmap to do the clearing it can
overrun the allocated buffer if we're not actually going to shrink it
and the last bit's address is on the chunk boundary.

Fix it by returning in that corner case and add few more tests to be
sure.

Closes: https://gitlab.com/libvirt/libvirt/-/issues/673
Fixes: d6e582da80
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
This commit is contained in:
Peter Krempa 2024-09-09 16:46:03 +02:00 committed by Pavel Hrdina
parent bc02cb9506
commit 8e28f2c5c2
2 changed files with 39 additions and 6 deletions
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6
src/util/virbitmap.c
View File

@ -1183,6 +1183,12 @@ virBitmapShrink(virBitmap *map,
nl = map->nbits / VIR_BITMAP_BITS_PER_UNIT;
nb = map->nbits % VIR_BITMAP_BITS_PER_UNIT;
/* If we're at the end of the allocation the attempt to clear 'map->nbit'
* and further would be beyond the end of the bitmap */
if (nl >= map->map_alloc)
return;
map->map[nl] &= ((1UL << nb) - 1);
toremove = map->map_alloc - (nl + 1);

39
tests/virbitmaptest.c
View File

@ -577,18 +577,45 @@ test12b(const void *opaque G_GNUC_UNUSED)
{
g_autoptr(virBitmap) map = NULL;
if (!(map = virBitmapParseUnlimited("34,1023")))
if (!(map = virBitmapParseUnlimited("31,32,63,64,1023")))
return -1;
if (checkBitmap(map, "34,1023", 1024) < 0)
if (checkBitmap(map, "31-32,63-64,1023", 1024) < 0)
return -1;
virBitmapShrink(map, 35);
if (checkBitmap(map, "34", 35) < 0)
/* no shrink at full alloc */
virBitmapShrink(map, 1025);
if (checkBitmap(map, "31-32,63-64,1023", 1024) < 0)
return -1;
virBitmapShrink(map, 34);
if (checkBitmap(map, "", 34) < 0)
/* shrink at the end */
virBitmapShrink(map, 1023);
if (checkBitmap(map, "31-32,63-64", 1023) < 0)
return -1;
/* extend back to see whether tail was cleared */
virBitmapSetBitExpand(map, 1022);
if (checkBitmap(map, "31-32,63-64,1022", 1023) < 0)
return -1;
virBitmapShrink(map, 64);
if (checkBitmap(map, "31-32,63", 64) < 0)
return -1;
virBitmapShrink(map, 65);
if (checkBitmap(map, "31-32,63", 64) < 0)
return -1;
virBitmapShrink(map, 63);
if (checkBitmap(map, "31-32", 63) < 0)
return -1;
virBitmapShrink(map, 32);
if (checkBitmap(map, "31", 32) < 0)
return -1;
virBitmapShrink(map, 31);
if (checkBitmap(map, "", 31) < 0)
return -1;
return 0;