netdev - [PATCH v1 net 13/16] cipso: Fix a data-race around cipso_v4_cache

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Date:   Tue, 5 Jul 2022 22:21:27 -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>,
        Paul Moore <paul.moore@...com>
Subject: [PATCH v1 net 13/16] cipso: Fix a data-race around cipso_v4_cache_bucketsize.

While reading cipso_v4_cache_bucketsize, it can be changed concurrently.
So, we need to add READ_ONCE().  Then we can set proc_dointvec_lockless()
as the handler to mark it safe.

Fixes: 446fda4f2682 ("[NetLabel]: CIPSOv4 engine")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
CC: Paul Moore <paul.moore@...com>
---
 Documentation/networking/ip-sysctl.rst |  2 +-
 net/ipv4/cipso_ipv4.c                  | 12 ++++++------
 net/ipv4/sysctl_net_ipv4.c             |  2 +-
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 9f41961d11d5..0e58001f8580 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -1085,7 +1085,7 @@ cipso_cache_enable - BOOLEAN
 cipso_cache_bucket_size - INTEGER
 	The CIPSO label cache consists of a fixed size hash table with each
 	hash bucket containing a number of cache entries.  This variable limits
-	the number of entries in each hash bucket; the larger the value the
+	the number of entries in each hash bucket; the larger the value is, the
 	more CIPSO label mappings that can be cached.  When the number of
 	entries in a given hash bucket reaches this limit adding new entries
 	causes the oldest entry in the bucket to be removed to make room.
diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index 62d5f99760aa..0600e9b06e1a 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -296,13 +296,13 @@ static int cipso_v4_cache_check(const unsigned char *key,
 int cipso_v4_cache_add(const unsigned char *cipso_ptr,
 		       const struct netlbl_lsm_secattr *secattr)
 {
-	int ret_val = -EPERM;
-	u32 bkt;
-	struct cipso_v4_map_cache_entry *entry = NULL;
+	int bkt_size = READ_ONCE(cipso_v4_cache_bucketsize);
 	struct cipso_v4_map_cache_entry *old_entry = NULL;
-	u32 cipso_ptr_len;
+	struct cipso_v4_map_cache_entry *entry = NULL;
+	u32 bkt, cipso_ptr_len;
+	int ret_val = -EPERM;
 
-	if (!cipso_v4_cache_enabled || cipso_v4_cache_bucketsize <= 0)
+	if (!cipso_v4_cache_enabled || bkt_size <= 0)
 		return 0;
 
 	cipso_ptr_len = cipso_ptr[1];
@@ -322,7 +322,7 @@ int cipso_v4_cache_add(const unsigned char *cipso_ptr,
 
 	bkt = entry->hash & (CIPSO_V4_CACHE_BUCKETS - 1);
 	spin_lock_bh(&cipso_v4_cache[bkt].lock);
-	if (cipso_v4_cache[bkt].size < cipso_v4_cache_bucketsize) {
+	if (cipso_v4_cache[bkt].size < bkt_size) {
 		list_add(&entry->list, &cipso_v4_cache[bkt].list);
 		cipso_v4_cache[bkt].size += 1;
 	} else {
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 0287d55f9230..5cd32b33bbac 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -527,7 +527,7 @@ static struct ctl_table ipv4_table[] = {
 		.data		= &cipso_v4_cache_bucketsize,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_lockless,
 	},
 	{
 		.procname	= "cipso_rbm_optfmt",
-- 
2.30.2