From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35365) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ctzzK-0002w4-Cg for qemu-devel@nongnu.org; Fri, 31 Mar 2017 13:05:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ctzzJ-00042F-7Q for qemu-devel@nongnu.org; Fri, 31 Mar 2017 13:05:26 -0400 From: Max Reitz Date: Fri, 31 Mar 2017 19:05:12 +0200 Message-Id: <20170331170512.10381-1-mreitz@redhat.com> Subject: [Qemu-devel] [PATCH for-2.9] block/parallels: Avoid overflows List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, Max Reitz , Stefan Hajnoczi , "Denis V . Lunev" , Kevin Wolf , Peter Maydell 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 --- 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