From: YiFei Zhu zhuyifei1999@gmail.com
[ Upstream commit 0f5d82f187e1beda3fe7295dfc500af266a5bd80 ]
Added a check in the switch case on start_header that checks for the existence of the header, and in the case that MAC is not set and the caller requests for MAC, -EFAULT. If the caller requests for NET then MAC's existence is completely ignored.
There is no function to check NET header's existence and as far as cgroup_skb/egress is concerned it should always be set.
Removed for ptr >= the start of header, considering offset is bounded unsigned and should always be true. len <= end - mac is redundant to ptr + len <= end.
Fixes: 3eee1f75f2b9 ("bpf: fix bpf_skb_load_bytes_relative pkt length check") Signed-off-by: YiFei Zhu zhuyifei@google.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: Stanislav Fomichev sdf@google.com Link: https://lore.kernel.org/bpf/76bb820ddb6a95f59a772ecbd8c8a336f646b362.1591812... Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/filter.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c index 11b97c31bca58..9512a9772d691 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1766,25 +1766,27 @@ BPF_CALL_5(bpf_skb_load_bytes_relative, const struct sk_buff *, skb, u32, offset, void *, to, u32, len, u32, start_header) { u8 *end = skb_tail_pointer(skb); - u8 *net = skb_network_header(skb); - u8 *mac = skb_mac_header(skb); - u8 *ptr; + u8 *start, *ptr;
- if (unlikely(offset > 0xffff || len > (end - mac))) + if (unlikely(offset > 0xffff)) goto err_clear;
switch (start_header) { case BPF_HDR_START_MAC: - ptr = mac + offset; + if (unlikely(!skb_mac_header_was_set(skb))) + goto err_clear; + start = skb_mac_header(skb); break; case BPF_HDR_START_NET: - ptr = net + offset; + start = skb_network_header(skb); break; default: goto err_clear; }
- if (likely(ptr >= mac && ptr + len <= end)) { + ptr = start + offset; + + if (likely(ptr + len <= end)) { memcpy(to, ptr, len); return 0; }