linux-kernel - [PATCH 2/5] tcp/md5: Don't leak ahash in OOM

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Date:   Fri,  5 Nov 2021 01:49:50 +0000
From:   Dmitry Safonov <dima@...sta.com>
To:     linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <0x7f454c46@...il.com>,
        Dmitry Safonov <dima@...sta.com>,
        Andy Lutomirski <luto@...capital.net>,
        David Ahern <dsahern@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Francesco Ruggeri <fruggeri@...sta.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Leonard Crestez <cdleonard@...il.com>,
        linux-crypto@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH 2/5] tcp/md5: Don't leak ahash in OOM

In quite unlikely scenario when __tcp_alloc_md5sig_pool() succeeded in
crypto_alloc_ahash(), but later failed to allocate per-cpu request or
scratch area ahash will be leaked.
In theory it can happen multiple times in OOM condition for every
setsockopt(TCP_MD5SIG{,_EXT}).

Add a clean-up path to free ahash.

Signed-off-by: Dmitry Safonov <dima@...sta.com>
---
 net/ipv4/tcp.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c0856a6af9f5..eb478028b1ea 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4276,15 +4276,13 @@ static void __tcp_alloc_md5sig_pool(void)
 					       GFP_KERNEL,
 					       cpu_to_node(cpu));
 			if (!scratch)
-				return;
+				goto out_free;
 			per_cpu(tcp_md5sig_pool, cpu).scratch = scratch;
 		}
-		if (per_cpu(tcp_md5sig_pool, cpu).md5_req)
-			continue;
 
 		req = ahash_request_alloc(hash, GFP_KERNEL);
 		if (!req)
-			return;
+			goto out_free;
 
 		ahash_request_set_callback(req, 0, NULL, NULL);
 
@@ -4295,6 +4293,16 @@ static void __tcp_alloc_md5sig_pool(void)
 	 */
 	smp_wmb();
 	tcp_md5sig_pool_populated = true;
+	return;
+
+out_free:
+	for_each_possible_cpu(cpu) {
+		if (per_cpu(tcp_md5sig_pool, cpu).md5_req == NULL)
+			break;
+		ahash_request_free(per_cpu(tcp_md5sig_pool, cpu).md5_req);
+		per_cpu(tcp_md5sig_pool, cpu).md5_req = NULL;
+	}
+	crypto_free_ahash(hash);
 }
 
 bool tcp_alloc_md5sig_pool(void)
-- 
2.33.1