[Patch] sysctl: forbid too long numbers

[Amerigo Wang <amwang@redhat.com>]

For some file under /proc/sys/kernel, the valid values for them
are < ULONG_MAX if they don't have they own max value defined. Thus,
numbers longer than are invalid.

So use strict_strtoul() instead of simple_strtoul(), and
make strict_strtoul() more strict.

[I don't know whom I should Cc...]
Signed-off-by: WANG Cong <amwang@redhat.com>

---
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index ab462b9..bc27e00 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2331,7 +2331,8 @@ static int __do_proc_dointvec(void *tbl_data, struct ctl_table *table,
 			if (*p < '0' || *p > '9')
 				break;
 
-			lval = simple_strtoul(p, &p, 0);
+			if (strict_strtoul(p, 0, &lval))
+				return -EINVAL;
 
 			len = p-buf;
 			if ((len < left) && *p && !isspace(*p))
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 756ccaf..ff2ca5c 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -163,11 +163,14 @@ int strict_strtoul(const char *cp, unsigned int base, unsigned long *res)
 	char *tail;
 	unsigned long val;
 	size_t len;
+	char tmp[32];
 
 	*res = 0;
 	len = strlen(cp);
 	if (len == 0)
 		return -EINVAL;
+	if (len > snprintf(tmp, "%ld", ULONG_MAX))
+		return -EINVAL;
 
 	val = simple_strtoul(cp, &tail, base);
 	if (tail == cp)