From: Stanislav Fomichev <sdf@google.com>
Date: Tue, 18 Apr 2023 15:53:38 -0700
Subject: [PATCH] bpf: Don't EFAULT for getsockopt with optval=NULL
References: bsc#1012628
Patch-mainline: 6.3.2
Git-commit: 00e74ae0863827d944e36e56a4ce1e77e50edb91

[ Upstream commit 00e74ae0863827d944e36e56a4ce1e77e50edb91 ]

Some socket options do getsockopt with optval=NULL to estimate the size
of the final buffer (which is returned via optlen). This breaks BPF
getsockopt assumptions about permitted optval buffer size. Let's enforce
these assumptions only when non-NULL optval is provided.

Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
Reported-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/ZD7Js4fj5YyI2oLd@google.com/T/#mb68daf700f87a9244a15d01d00c3f0e5b08f49f7
Link: https://lore.kernel.org/bpf/20230418225343.553806-2-sdf@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 kernel/bpf/cgroup.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index bf2fdb33..819f011f 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1921,14 +1921,17 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
 	if (ret < 0)
 		goto out;
 
-	if (ctx.optlen > max_optlen || ctx.optlen < 0) {
+	if (optval && (ctx.optlen > max_optlen || ctx.optlen < 0)) {
 		ret = -EFAULT;
 		goto out;
 	}
 
 	if (ctx.optlen != 0) {
-		if (copy_to_user(optval, ctx.optval, ctx.optlen) ||
-		    put_user(ctx.optlen, optlen)) {
+		if (optval && copy_to_user(optval, ctx.optval, ctx.optlen)) {
+			ret = -EFAULT;
+			goto out;
+		}
+		if (put_user(ctx.optlen, optlen)) {
 			ret = -EFAULT;
 			goto out;
 		}
-- 
2.35.3