netdev - [PATCH -next V2] sysctl: returns -EINVAL when a negative value is passed to proc_doulongvec

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Date:   Mon, 20 Dec 2021 17:26:27 +0800
From:   Baokun Li <libaokun1@...wei.com>
To:     <mcgrof@...nel.org>, <akpm@...ux-foundation.org>,
        <keescook@...omium.org>, <yzaikin@...gle.com>, <ast@...nel.org>,
        <daniel@...earbox.net>, <andrii@...nel.org>, <kafai@...com>,
        <songliubraving@...com>, <yhs@...com>, <john.fastabend@...il.com>,
        <kpsingh@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <netdev@...r.kernel.org>, <bpf@...r.kernel.org>,
        <libaokun1@...wei.com>, <yukuai3@...wei.com>,
        Hulk Robot <hulkci@...wei.com>
Subject: [PATCH -next V2] sysctl: returns -EINVAL when a negative value is passed to proc_doulongvec_minmax

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.

Reported-by: Hulk Robot <hulkci@...wei.com>
Signed-off-by: Baokun Li <libaokun1@...wei.com>
---
V1->V2:
	Modify the judgment position.

 kernel/sysctl.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 7f07b058b180..4211e39a5fd3 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1147,10 +1147,11 @@ 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;
-- 
2.31.1