[PATCH 3.16 113/129] kernel/sysctl.c: add missing range check in do_proc_dointvec_minmax_conv

[Ben Hutchings]

3.16.70-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Zev Weiss <zev@xxxxxxxxxxxxxxxxx>

commit 8cf7630b29701d364f8df4a50e4f1f5e752b2778 upstream.

This bug has apparently existed since the introduction of this function
in the pre-git era (4500e91754d3 in Thomas Gleixner's history.git,
"[NET]: Add proc_dointvec_userhz_jiffies, use it for proper handling of
neighbour sysctls.").

As a minimal fix we can simply duplicate the corresponding check in
do_proc_dointvec_conv().

Link: http://lkml.kernel.org/r/20190207123426.9202-3-zev@xxxxxxxxxxxxxxxxx
Signed-off-by: Zev Weiss <zev@xxxxxxxxxxxxxxxxx>
Cc: Brendan Higgins <brendanhiggins@xxxxxxxxxx>
Cc: Iurii Zaikin <yzaikin@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 kernel/sysctl.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2179,7 +2179,16 @@ static int do_proc_dointvec_minmax_conv(
 {
 	struct do_proc_dointvec_minmax_conv_param *param = data;
 	if (write) {
-		int val = *negp ? -*lvalp : *lvalp;
+		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))
 			return -EINVAL;