From f4fc43fde12a1b87b0433a9f8e6ad6fb5fe9cd8a Mon Sep 17 00:00:00 2001 From: Stanislav Fomichev Date: Tue, 18 Apr 2023 15:53:38 -0700 Subject: [PATCH] bpf: Don't EFAULT for getsockopt with optval=NULL [ 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 Signed-off-by: Stanislav Fomichev Signed-off-by: Daniel Borkmann 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 --- 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 6d92e393e1bc..d3593a520bb7 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -1516,7 +1516,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, goto out; } - if (ctx.optlen > max_optlen || ctx.optlen < 0) { + if (optval && (ctx.optlen > max_optlen || ctx.optlen < 0)) { ret = -EFAULT; goto out; } @@ -1530,8 +1530,11 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, } 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; }