From ab21c1b5f799395232b838e98981cfed6d647905 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Wed, 24 Oct 2018 22:05:44 +0200 Subject: [PATCH] bpf: disallow direct packet access for unpriv in cg_skb Commit b39b5f411dcf ("bpf: add cg_skb_is_valid_access for BPF_PROG_TYPE_CGROUP_SKB") added support for returning pkt pointers for direct packet access. Given this program type is allowed for both unprivileged and privileged users, we shouldn't allow unprivileged ones to use it, e.g. besides others one reason would be to avoid any potential speculation on the packet test itself, thus guard this for root only. Fixes: b39b5f411dcf ("bpf: add cg_skb_is_valid_access for BPF_PROG_TYPE_CGROUP_SKB") Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Cc: Song Liu Signed-off-by: Alexei Starovoitov --- net/core/filter.c | 6 ++++++ tools/testing/selftests/bpf/test_verifier.c | 2 +- 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/net/core/filter.c b/net/core/filter.c index 35c6933c2622..3fdddfa9a0fd 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5496,7 +5496,13 @@ static bool cg_skb_is_valid_access(int off, int size, case bpf_ctx_range(struct __sk_buff, data_meta): case bpf_ctx_range(struct __sk_buff, flow_keys): return false; + case bpf_ctx_range(struct __sk_buff, data): + case bpf_ctx_range(struct __sk_buff, data_end): + if (!capable(CAP_SYS_ADMIN)) + return false; + break; } + if (type == BPF_WRITE) { switch (off) { case bpf_ctx_range(struct __sk_buff, mark): diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index 8e1a79d2792c..36f3d3009d1a 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -4892,7 +4892,7 @@ static struct bpf_test tests[] = { }, .result = ACCEPT, .result_unpriv = REJECT, - .errstr_unpriv = "R3 pointer comparison prohibited", + .errstr_unpriv = "invalid bpf_context access off=76 size=4", .prog_type = BPF_PROG_TYPE_CGROUP_SKB, }, {