[CCID3] Avoid unsigned integer overflows in usecs_div
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 7bf3b3a..ae0500c 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -43,12 +43,22 @@
#include "ccid3.h"
/*
- * Reason for maths with 10 here is to avoid 32 bit overflow when a is big.
+ * Reason for maths here is to avoid 32 bit overflow when a is big.
+ * With this we get close to the limit.
*/
static inline u32 usecs_div(const u32 a, const u32 b)
{
- const u32 tmp = a * (USEC_PER_SEC / 10);
- return b > 20 ? tmp / (b / 10) : tmp;
+ const u32 div = a < (UINT_MAX / (USEC_PER_SEC / 10)) ? 10 :
+ a < (UINT_MAX / (USEC_PER_SEC / 50)) ? 50 :
+ a < (UINT_MAX / (USEC_PER_SEC / 100)) ? 100 :
+ a < (UINT_MAX / (USEC_PER_SEC / 500)) ? 500 :
+ a < (UINT_MAX / (USEC_PER_SEC / 1000)) ? 1000 :
+ a < (UINT_MAX / (USEC_PER_SEC / 5000)) ? 5000 :
+ a < (UINT_MAX / (USEC_PER_SEC / 10000)) ? 10000 :
+ a < (UINT_MAX / (USEC_PER_SEC / 50000)) ? 50000 :
+ 100000;
+ const u32 tmp = a * (USEC_PER_SEC / div);
+ return (b >= 2 * div) ? tmp / (b / div) : tmp;
}
static int ccid3_debug;