[PATCH 5.10 08/43] bpf: Dont leak memory in bpf getsockopt when optlen == 0

[Greg Kroah-Hartman]

From: Stanislav Fomichev <s...@google.com>

commit 4be34f3d0731b38a1b24566b37fbb39500aaf3a2 upstream.

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.

Fixes: d8fe449a9c51 ("bpf: Don't return EINVAL from {get,set}sockopt when 
optlen > PAGE_SIZE")
Reported-by: Martin KaFai Lau <ka...@fb.com>
Signed-off-by: Stanislav Fomichev <s...@google.com>
Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
Acked-by: Martin KaFai Lau <ka...@fb.com>
Link: https://lore.kernel.org/bpf/20210112162829.775079-1-...@google.com
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 kernel/bpf/cgroup.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1391,12 +1391,13 @@ int __cgroup_bpf_run_filter_setsockopt(s
                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;
 }