sysctl: returns -EINVAL when a negative value is passed to proc_doulongvec_minmax

mainline inclusion
from mainline-5.17-rc1
commit 1622ed7d
category: bugfix
bugzilla: 185873, https://gitee.com/openeuler/kernel/issues/I4MTTR
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1622ed7d0743201293094162c26019d2573ecacb

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

When we pass a negative value to the proc_doulongvec_minmax() function,
the function returns 0, but the corresponding interface value does not
change.

we can easily reproduce this problem with the following commands:

    cd /proc/sys/fs/epoll
    echo -1 > max_user_watches; echo $?; cat max_user_watches

This function requires a non-negative number to be passed in, so when a
negative number is passed in, -EINVAL is returned.

Link: https://lkml.kernel.org/r/20211220092627.3744624-1-libaokun1@huawei.comSigned-off-by: NBaokun Li <libaokun1@huawei.com>
Reported-by: NHulk Robot <hulkci@huawei.com>
Acked-by: NLuis Chamberlain <mcgrof@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NBaokun Li <libaokun1@huawei.com>
Reviewed-by: NZhang Yi <yi.zhang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

kernel/sysctl.c

@@ -1186,10 +1186,11 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table,
 			err = proc_get_long(&p, &left, &val, &neg,
 					     proc_wspace_sep,
 					     sizeof(proc_wspace_sep), NULL);
-			if (err)
+			if (err || neg) {
+				err = -EINVAL;
 				break;
-			if (neg)
-				continue;
+			}
+
 			val = convmul * val / convdiv;
 			if ((min && val < *min) || (max && val > *max)) {
 				err = -EINVAL;