1 files changed, 13 insertions, 5 deletions

diff --git a/lib/kstrtox.c b/lib/kstrtox.c
index 7a94c8f14e29..b1dd3e7d88cb 100644
--- a/lib/kstrtox.c
+++ b/lib/kstrtox.c
@@ -44,12 +44,13 @@ const char *_parse_integer_fixup_radix(const char *s, unsigned int *base)
  *
  * Don't you dare use this function.
  */
-unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *res)
+unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long *p)
 {
+        unsigned long long res;
         unsigned int rv;
         int overflow;
 
-        *res = 0;
+        res = 0;
         rv = 0;
         overflow = 0;
         while (*s) {
@@ -64,12 +65,19 @@ unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long
 
                 if (val >= base)
                         break;
-                if (*res > div_u64(ULLONG_MAX - val, base))
-                        overflow = 1;
-                *res = *res * base + val;
+                /*
+                 * Check for overflow only if we are within range of
+                 * it in the max base we support (16)
+                 */
+                if (unlikely(res & (~0ull << 60))) {
+                        if (res > div_u64(ULLONG_MAX - val, base))
+                                overflow = 1;
+                }
+                res = res * base + val;
                 rv++;
                 s++;
         }
+        *p = res;
         if (overflow)
                 rv |= KSTRTOX_OVERFLOW;
         return rv;