kernel/sysctl.c: add missing range check in do_proc_dointvec_minmax_conv

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@bewilderbeest.net
Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: <stable@vger.kernel.org>	[2.6.2+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 7bb3988425ee..0854197e0e67 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2645,7 +2645,16 @@ static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp,
 {
         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;