[PATCH bpf v2] bpf: don't leak memory in bpf getsockopt when optlen == 0

[Stanislav Fomichev <sdf@google.com>]

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@fb.com>
Fixes: d8fe449a9c51 ("bpf: Don't return EINVAL from {get,set}sockopt when optlen > PAGE_SIZE")
Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
 kernel/bpf/cgroup.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 6ec088a96302..96555a8a2c54 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1391,12 +1391,13 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level,
 		if (ctx.optlen != 0) {
 			*optlen = ctx.optlen;
 			*kernel_optval = ctx.optval;
+			/* export and don't free sockopt buf */
+			return 0;
 		}
 	}
 
 out:
-	if (ret)
-		sockopt_free_buf(&ctx);
+	sockopt_free_buf(&ctx);
 	return ret;
 }
 
-- 
2.30.0.284.gd98b1dd5eaa7-goog