netdev - [PATCH bpf] bpf: don't leak memory in bpf getsockopt when optlen == 0

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Message-Id: <20210111194738.132139-1-sdf@google.com>
Date:   Mon, 11 Jan 2021 11:47:38 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     netdev@...r.kernel.org, bpf@...r.kernel.org
Cc:     ast@...nel.org, daniel@...earbox.net,
        Stanislav Fomichev <sdf@...gle.com>,
        Martin KaFai Lau <kafai@...com>
Subject: [PATCH bpf] bpf: don't leak memory in bpf getsockopt when optlen == 0

optlen == 0 indicates that the kernel should ignore BPF buffer
and use the original one from the user. We, however, forget
to free the temporary buffer that we've allocated for BPF.

Reported-by: Martin KaFai Lau <kafai@...com>
Fixes: d8fe449a9c51 ("bpf: Don't return EINVAL from {get,set}sockopt when optlen > PAGE_SIZE")
Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
---
 kernel/bpf/cgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 6ec088a96302..09179ab72c03 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1395,7 +1395,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level,
 	}
 
 out:
-	if (ret)
+	if (*kernel_optval == NULL)
 		sockopt_free_buf(&ctx);
 	return ret;
 }
-- 
2.30.0.284.gd98b1dd5eaa7-goog