[PATCH] proc: fix /proc/*/map_files lookup some more

[Alexey Dobriyan <adobriyan@gmail.com>]

I totally forgot that _parse_integer() accepts arbitrary amount of
leading zeroes leading to the following:

		OK
	# readlink /proc/1/map_files/56427ecba000-56427eddc000
	/lib/systemd/systemd

		bogus
	# readlink /proc/1/map_files/00000000000056427ecba000-56427eddc000
	/lib/systemd/systemd
	# readlink /proc/1/map_files/56427ecba000-00000000000056427eddc000
	/lib/systemd/systemd

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 fs/proc/base.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1913,9 +1913,11 @@ static int dname_to_vma_addr(struct dentry *dentry,
 			     unsigned long *start, unsigned long *end)
 {
 	const char *str = dentry->d_name.name;
+	unsigned int len = dentry->d_name.len;
 	unsigned long long sval, eval;
-	unsigned int len;
 
+	if (len > 1 && *str == '0')
+		return -EINVAL;
 	len = _parse_integer(str, 16, &sval);
 	if (len & KSTRTOX_OVERFLOW)
 		return -EINVAL;
@@ -1927,6 +1929,9 @@ static int dname_to_vma_addr(struct dentry *dentry,
 		return -EINVAL;
 	str++;
 
+	len = strlen(str);
+	if (len > 1 && *str == '0')
+		return -EINVAL;
 	len = _parse_integer(str, 16, &eval);
 	if (len & KSTRTOX_OVERFLOW)
 		return -EINVAL;