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authorMax Reitz <mreitz@redhat.com>2014-04-29 19:03:14 +0200
committerKevin Wolf <kwolf@redhat.com>2014-04-30 14:46:17 +0200
commitb93f995081cc32e56071fef179161d2907d0491e (patch)
treec4a4a5ab3111109055ffac05634c2d298b44b4e9 /block/qcow2-cluster.c
parenta49139af77850d64d74f9ffe43cabe7aa4f19de0 (diff)
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qcow2: Check min_size in qcow2_grow_l1_table()
First, new_l1_size is an int64_t, whereas min_size is a uint64_t. Therefore, during the loop which adjusts new_l1_size until it equals or exceeds min_size, new_l1_size might overflow and become negative. The comparison in the loop condition however will take it as an unsigned value (because min_size is unsigned) and therefore recognize it as exceeding min_size. Therefore, the loop is left with a negative new_l1_size, which is not correct. This could be fixed by making new_l1_size uint64_t. On the other hand, however, by doing this, the while loop may take forever. If min_size is e.g. UINT64_MAX, it will take new_l1_size probably multiple overflows to reach the exact same value (if it reaches it at all). Then, right after the loop, new_l1_size will be recognized as being too big anyway. Both problems require a ridiculously high min_size value, which is very unlikely to occur; but both problems are also simply avoided by checking whether min_size is sane before calculating new_l1_size (which should still be checked separately, though). Signed-off-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block/qcow2-cluster.c')
-rw-r--r--block/qcow2-cluster.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index b746429..76d2bcf 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -42,6 +42,13 @@ int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
if (min_size <= s->l1_size)
return 0;
+ /* Do a sanity check on min_size before trying to calculate new_l1_size
+ * (this prevents overflows during the while loop for the calculation of
+ * new_l1_size) */
+ if (min_size > INT_MAX / sizeof(uint64_t)) {
+ return -EFBIG;
+ }
+
if (exact_size) {
new_l1_size = min_size;
} else {