5.4-stable review patch. If anyone has any objections, please let me know.
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From: Cong Wang cong.wang@bytedance.com
[ Upstream commit 9ecc4d858b92c1bb0673ad9c327298e600c55659 ]
skb_network_offset() and skb_transport_offset() can be negative when they are called after we pull the transport header, for example, when we use eBPF sockmap at the point of ->sk_data_ready().
__bpf_skb_min_len() uses an unsigned int to get these offsets, this leads to a very large number which then causes bpf_skb_change_tail() failed unexpectedly.
Fix this by using a signed int to get these offsets and ensure the minimum is at least zero.
Fixes: 5293efe62df8 ("bpf: add bpf_skb_change_tail helper") Signed-off-by: Cong Wang cong.wang@bytedance.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: John Fastabend john.fastabend@gmail.com Link: https://lore.kernel.org/bpf/20241213034057.246437-2-xiyou.wangcong@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/filter.c | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c index 9f67d9f20ae0..6ba1121a9f34 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -3252,13 +3252,22 @@ static const struct bpf_func_proto bpf_skb_adjust_room_proto = {
static u32 __bpf_skb_min_len(const struct sk_buff *skb) { - u32 min_len = skb_network_offset(skb); - - if (skb_transport_header_was_set(skb)) - min_len = skb_transport_offset(skb); - if (skb->ip_summed == CHECKSUM_PARTIAL) - min_len = skb_checksum_start_offset(skb) + - skb->csum_offset + sizeof(__sum16); + int offset = skb_network_offset(skb); + u32 min_len = 0; + + if (offset > 0) + min_len = offset; + if (skb_transport_header_was_set(skb)) { + offset = skb_transport_offset(skb); + if (offset > 0) + min_len = offset; + } + if (skb->ip_summed == CHECKSUM_PARTIAL) { + offset = skb_checksum_start_offset(skb) + + skb->csum_offset + sizeof(__sum16); + if (offset > 0) + min_len = offset; + } return min_len; }