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

Dmitry Safonov
2021-11-05T01:50:06Z

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@arista.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