kernel/sysctl.c: define minmax conv functions in terms of non-minmax …

…versions

do_proc_do[u]intvec_minmax_conv() had included open-coded versions of
do_proc_do[u]intvec_conv(); the duplication led to buggy inconsistencies
(missing range checks).  To reduce the likelihood of such problems in the
future, we can instead refactor both to be defined in terms of their
non-bounded counterparts (plus the added check).

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Zev Weiss <[email protected]>
Cc: Brendan Higgins <[email protected]>
Cc: Iurii Zaikin <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Luis Chamberlain <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

kernel/sysctl.c

@@ -2643,32 +2643,25 @@ static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp,
 					int *valp,
 					int write, void *data)
 {
+	int tmp, ret;
 	struct do_proc_dointvec_minmax_conv_param *param = data;
+	/*
+	 * If writing, first do so via a temporary local int so we can
+	 * bounds-check it before touching *valp.
+	 */
+	int *ip = write ? &tmp : valp;
+
+	ret = do_proc_dointvec_conv(negp, lvalp, ip, write, data);
+	if (ret)
+		return ret;
+
 	if (write) {
-		int val;
-		if (*negp) {
-			if (*lvalp > (unsigned long) INT_MAX + 1)
-				return -EINVAL;
-			val = -*lvalp;
-		} else {
-			if (*lvalp > (unsigned long) INT_MAX)
-				return -EINVAL;
-			val = *lvalp;
-		}
-		if ((param->min && *param->min > val) ||
-		    (param->max && *param->max < val))
+		if ((param->min && *param->min > tmp) ||
+		    (param->max && *param->max < tmp))
 			return -EINVAL;
-		*valp = val;
-	} else {
-		int val = *valp;
-		if (val < 0) {
-			*negp = true;
-			*lvalp = -(unsigned long)val;
-		} else {
-			*negp = false;
-			*lvalp = (unsigned long)val;
-		}
+		*valp = tmp;
 	}
+
 	return 0;
 }
 
@@ -2717,22 +2710,22 @@ static int do_proc_douintvec_minmax_conv(unsigned long *lvalp,
 					 unsigned int *valp,
 					 int write, void *data)
 {
+	int ret;
+	unsigned int tmp;
 	struct do_proc_douintvec_minmax_conv_param *param = data;
+	/* write via temporary local uint for bounds-checking */
+	unsigned int *up = write ? &tmp : valp;
 
-	if (write) {
-		unsigned int val = *lvalp;
+	ret = do_proc_douintvec_conv(lvalp, up, write, data);
+	if (ret)
+		return ret;
 
-		if (*lvalp > UINT_MAX)
-			return -EINVAL;
-
-		if ((param->min && *param->min > val) ||
-		    (param->max && *param->max < val))
+	if (write) {
+		if ((param->min && *param->min > tmp) ||
+		    (param->max && *param->max < tmp))
 			return -ERANGE;
 
-		*valp = val;
-	} else {
-		unsigned int val = *valp;
-		*lvalp = (unsigned long) val;
+		*valp = tmp;
 	}
 
 	return 0;