linux-kernel - [PATCH v1 net 15/16] icmp: Fix data-races around sysctl.

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Message-ID: <20220706052130.16368-16-kuniyu@amazon.com>
Date:   Tue, 5 Jul 2022 22:21:29 -0700
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>
CC:     Kuniyuki Iwashima <kuniyu@...zon.com>,
        Kuniyuki Iwashima <kuni1840@...il.com>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v1 net 15/16] icmp: Fix data-races around sysctl.

While reading sysctl variables, it can be changed concurrently.  So, we
need to add READ_ONCE().  Then we can set proc_dointvec_minmax_lockless()
as the handler to mark it safe.

Fixes: 4cdf507d5452 ("icmp: add a global rate limitation")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 net/ipv4/icmp.c            | 5 +++--
 net/ipv4/sysctl_net_ipv4.c | 4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index efea0e796f06..0f9e61d29f73 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -253,11 +253,12 @@ bool icmp_global_allow(void)
 	spin_lock(&icmp_global.lock);
 	delta = min_t(u32, now - icmp_global.stamp, HZ);
 	if (delta >= HZ / 50) {
-		incr = sysctl_icmp_msgs_per_sec * delta / HZ ;
+		incr = READ_ONCE(sysctl_icmp_msgs_per_sec) * delta / HZ;
 		if (incr)
 			WRITE_ONCE(icmp_global.stamp, now);
 	}
-	credit = min_t(u32, icmp_global.credit + incr, sysctl_icmp_msgs_burst);
+	credit = min_t(u32, icmp_global.credit + incr,
+		       READ_ONCE(sysctl_icmp_msgs_burst));
 	if (credit) {
 		/* We want to use a credit of one in average, but need to randomize
 		 * it for security reasons.
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 706795a3b369..3b1d18be0857 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -555,7 +555,7 @@ static struct ctl_table ipv4_table[] = {
 		.data		= &sysctl_icmp_msgs_per_sec,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
+		.proc_handler	= proc_dointvec_minmax_lockless,
 		.extra1		= SYSCTL_ZERO,
 	},
 	{
@@ -563,7 +563,7 @@ static struct ctl_table ipv4_table[] = {
 		.data		= &sysctl_icmp_msgs_burst,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
+		.proc_handler	= proc_dointvec_minmax_lockless,
 		.extra1		= SYSCTL_ZERO,
 	},
 	{
-- 
2.30.2