[PATCH 5.1 006/155] sysctl: return -EINVAL if val violates minmax

[Greg Kroah-Hartman]

[ Upstream commit e260ad01f0aa9e96b5386d5cd7184afd949dc457 ]

Currently when userspace gives us a values that overflow e.g.  file-max
and other callers of __do_proc_doulongvec_minmax() we simply ignore the
new value and leave the current value untouched.

This can be problematic as it gives the illusion that the limit has
indeed be bumped when in fact it failed.  This commit makes sure to
return EINVAL when an overflow is detected.  Please note that this is a
userspace facing change.

Link: http://lkml.kernel.org/r/20190210203943.8227-4-christian@xxxxxxxxxx
Signed-off-by: Christian Brauner <christian@xxxxxxxxxx>
Acked-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 kernel/sysctl.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c9ec050bcf46..387efbaf464a 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2874,8 +2874,10 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int
 			if (neg)
 				continue;
 			val = convmul * val / convdiv;
-			if ((min && val < *min) || (max && val > *max))
-				continue;
+			if ((min && val < *min) || (max && val > *max)) {
+				err = -EINVAL;
+				break;
+			}
 			*i = val;
 		} else {
 			val = convdiv * (*i) / convmul;
-- 
2.20.1