Re: [spice-server PATCH 1/3] red_get_surface_cmd: avoid overflow

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On 07/17/2017 11:22 AM, Frediano Ziglio wrote:

Although unlikely, theoretically, multiplying two 32-bit
numbers may overflow.

Found by coverity.

Signed-off-by: Uri Lublin <uril@xxxxxxxxxx>
---
  server/red-parse-qxl.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/server/red-parse-qxl.c b/server/red-parse-qxl.c
index 33f36923a..0ffa5f7d4 100644
--- a/server/red-parse-qxl.c
+++ b/server/red-parse-qxl.c
@@ -1397,7 +1397,7 @@ bool red_get_surface_cmd(RedMemSlotInfo *slots, int
group_id,
              return false;
          }
- size = red->u.surface_create.height *
abs(red->u.surface_create.stride);
+        size = red->u.surface_create.height *
(uint64_t)abs(red->u.surface_create.stride);
          red->u.surface_create.data =
              (uint8_t*)memslot_get_virt(slots, qxl->u.surface_create.data,
              size, group_id, &error);
          if (error) {

This overflow is already handled by red_validate_surface call.

Indeed.
I'll drop this patch.


Also note that silently the uint64_t size is converted to 32 bit calling
memslot_get_virt so maybe would be better to change size to uint32_t.

Frediano


Thanks,
    Uri.

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