Change the types of variables in allocate_clusters() to int64_t so we do
not have to worry about potential overflows.
Add an assertion that our accesses to s->bat[] do not result in a buffer
overflow and that the implicit conversion performed when invoking
bat_entry_off() does not result in an integer overflow.
Coverity-id: 1307776
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
This supercedes Peter's patch "block/parallels.c: avoid integer overflow
in allocate_clusters()".
---
block/parallels.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/block/parallels.c b/block/parallels.c
index 4173b3fb9d..90acf79687 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -192,8 +192,7 @@ static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, int *pnum)
{
BDRVParallelsState *s = bs->opaque;
- uint32_t idx, to_allocate, i;
- int64_t pos, space;
+ int64_t pos, space, idx, to_allocate, i;
pos = block_status(s, sector_num, nb_sectors, pnum);
if (pos > 0) {
@@ -201,11 +200,19 @@ static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num,
}
idx = sector_num / s->tracks;
- if (idx >= s->bat_size) {
- return -EINVAL;
- }
-
to_allocate = DIV_ROUND_UP(sector_num + *pnum, s->tracks) - idx;
+
+ /* This function is called only by parallels_co_writev(), which will never
+ * pass a sector_num at or beyond the end of the image (because the block
+ * layer never passes such a sector_num to that function). Therefore, idx
+ * is always below s->bat_size.
+ * block_status() will limit *pnum so that sector_num + *pnum will not
+ * exceed the image end. Therefore, idx + to_allocate cannot exceed
+ * s->bat_size.
+ * Note that s->bat_size is an unsigned int, therefore idx + to_allocate
+ * will always fit into a uint32_t. */
+ assert(idx < s->bat_size && idx + to_allocate <= s->bat_size);
+
space = to_allocate * s->tracks;
if (s->data_end + space > bdrv_getlength(bs->file->bs) >> BDRV_SECTOR_BITS) {
int ret;
--
2.12.1
On 03/31/2017 12:05 PM, Max Reitz wrote: > Change the types of variables in allocate_clusters() to int64_t so we do > not have to worry about potential overflows. > > Add an assertion that our accesses to s->bat[] do not result in a buffer > overflow and that the implicit conversion performed when invoking > bat_entry_off() does not result in an integer overflow. > > Coverity-id: 1307776 > Signed-off-by: Max Reitz <mreitz@redhat.com> > --- > This supercedes Peter's patch "block/parallels.c: avoid integer overflow > in allocate_clusters()". > --- > block/parallels.c | 19 +++++++++++++------ > 1 file changed, 13 insertions(+), 6 deletions(-) > Reviewed-by: Eric Blake <eblake@redhat.com> -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
On 03/31/2017 02:05 PM, Max Reitz wrote: > Change the types of variables in allocate_clusters() to int64_t so we do > not have to worry about potential overflows. > > Add an assertion that our accesses to s->bat[] do not result in a buffer > overflow and that the implicit conversion performed when invoking > bat_entry_off() does not result in an integer overflow. > > Coverity-id: 1307776 > Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> > --- > This supercedes Peter's patch "block/parallels.c: avoid integer overflow > in allocate_clusters()". > --- > block/parallels.c | 19 +++++++++++++------ > 1 file changed, 13 insertions(+), 6 deletions(-) > > diff --git a/block/parallels.c b/block/parallels.c > index 4173b3fb9d..90acf79687 100644 > --- a/block/parallels.c > +++ b/block/parallels.c > @@ -192,8 +192,7 @@ static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num, > int nb_sectors, int *pnum) > { > BDRVParallelsState *s = bs->opaque; > - uint32_t idx, to_allocate, i; > - int64_t pos, space; > + int64_t pos, space, idx, to_allocate, i; > > pos = block_status(s, sector_num, nb_sectors, pnum); > if (pos > 0) { > @@ -201,11 +200,19 @@ static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num, > } > > idx = sector_num / s->tracks; > - if (idx >= s->bat_size) { > - return -EINVAL; > - } > - > to_allocate = DIV_ROUND_UP(sector_num + *pnum, s->tracks) - idx; > + > + /* This function is called only by parallels_co_writev(), which will never > + * pass a sector_num at or beyond the end of the image (because the block > + * layer never passes such a sector_num to that function). Therefore, idx > + * is always below s->bat_size. > + * block_status() will limit *pnum so that sector_num + *pnum will not > + * exceed the image end. Therefore, idx + to_allocate cannot exceed > + * s->bat_size. > + * Note that s->bat_size is an unsigned int, therefore idx + to_allocate > + * will always fit into a uint32_t. */ > + assert(idx < s->bat_size && idx + to_allocate <= s->bat_size); > + > space = to_allocate * s->tracks; > if (s->data_end + space > bdrv_getlength(bs->file->bs) >> BDRV_SECTOR_BITS) { > int ret; >
On 31.03.2017 19:05, Max Reitz wrote: > Change the types of variables in allocate_clusters() to int64_t so we do > not have to worry about potential overflows. > > Add an assertion that our accesses to s->bat[] do not result in a buffer > overflow and that the implicit conversion performed when invoking > bat_entry_off() does not result in an integer overflow. > > Coverity-id: 1307776 > Signed-off-by: Max Reitz <mreitz@redhat.com> > --- > This supercedes Peter's patch "block/parallels.c: avoid integer overflow > in allocate_clusters()". > --- > block/parallels.c | 19 +++++++++++++------ > 1 file changed, 13 insertions(+), 6 deletions(-) Thanks for reviewing, applied to my block branch: https://github.com/XanClic/qemu/commits/block Max
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