From 0ba7a3ba6608de6e0c0bfe3009a63d7e0b7ab0ce Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Fri, 9 Sep 2005 02:28:47 -0300 Subject: [CCID3] Avoid unsigned integer overflows in usecs_div Signed-off-by: Arnaldo Carvalho de Melo --- net/dccp/ccids/ccid3.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) (limited to 'net/dccp/ccids') diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c index 7bf3b3a91e9..ae0500c79d0 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; -- cgit v1.2.3