[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 <z...@bewilderbeest.net>

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-...@bewilderbeest.net
Signed-off-by: Zev Weiss <z...@bewilderbeest.net>
Cc: Brendan Higgins <brendanhigg...@google.com>
Cc: Iurii Zaikin <yzai...@google.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Luis Chamberlain <mcg...@kernel.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
 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;