Commit 6f5a630d authored by Alexei Starovoitov's avatar Alexei Starovoitov
Browse files

bpf, net: Introduce skb_pointer_if_linear(). 



Network drivers always call skb_header_pointer() with non-null buffer.
Remove !buffer check to prevent accidental misuse of skb_header_pointer().
Introduce skb_pointer_if_linear() instead.

Reported-by: default avatarJakub Kicinski <kuba@kernel.org>
Acked-by: default avatarJakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20230718234021.43640-1-alexei.starovoitov@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 41ee0145

include/linux/skbuff.h

+9 −1
Original line number Diff line number Diff line
@@ -4023,7 +4023,7 @@ __skb_header_pointer(const struct sk_buff *skb, int offset, int len, 
	if (likely(hlen - offset >= len))

		return (void *)data + offset;



	if (!skb || !buffer || unlikely(skb_copy_bits(skb, offset, buffer, len) < 0))

	if (!skb || unlikely(skb_copy_bits(skb, offset, buffer, len) < 0))

		return NULL;



	return buffer;
@@ -4036,6 +4036,14 @@ skb_header_pointer(const struct sk_buff *skb, int offset, int len, void *buffer) 
				    skb_headlen(skb), buffer);

}



static inline void * __must_check

skb_pointer_if_linear(const struct sk_buff *skb, int offset, int len)

{

	if (likely(skb_headlen(skb) - offset >= len))

		return skb->data + offset;

	return NULL;

}



/**

 *	skb_needs_linearize - check if we need to linearize a given skb

 *			      depending on the given device features.

kernel/bpf/helpers.c

+4 −1
Original line number Diff line number Diff line
@@ -2263,7 +2263,10 @@ __bpf_kfunc void *bpf_dynptr_slice(const struct bpf_dynptr_kern *ptr, u32 offset 
	case BPF_DYNPTR_TYPE_RINGBUF:

		return ptr->data + ptr->offset + offset;

	case BPF_DYNPTR_TYPE_SKB:

		if (buffer__opt)

			return skb_header_pointer(ptr->data, ptr->offset + offset, len, buffer__opt);

		else

			return skb_pointer_if_linear(ptr->data, ptr->offset + offset, len);

	case BPF_DYNPTR_TYPE_XDP:

	{

		void *xdp_ptr = bpf_xdp_pointer(ptr->data, ptr->offset + offset, len);