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bpf, net: Introduce skb_pointer_if_linear().

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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: Jakub Kicinski <kuba@kernel.org>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20230718234021.43640-1-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Alexei Starovoitov 2023-07-18 16:40:21 -07:00
parent 41ee0145a4
commit 6f5a630d7c
2 changed files with 13 additions and 2 deletions
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10
include/linux/skbuff.h
View File

@ -4023,7 +4023,7 @@ __skb_header_pointer(const struct sk_buff *skb, int offset, int len,
if (likely(hlen - offset >= len)) if (likely(hlen - offset >= len))
return (void *)data + offset; 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 NULL;
return buffer; return buffer;
@ -4036,6 +4036,14 @@ skb_header_pointer(const struct sk_buff *skb, int offset, int len, void *buffer)
skb_headlen(skb), 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 * skb_needs_linearize - check if we need to linearize a given skb
* depending on the given device features. * depending on the given device features.

5
kernel/bpf/helpers.c
View File

@ -2263,7 +2263,10 @@ __bpf_kfunc void *bpf_dynptr_slice(const struct bpf_dynptr_kern *ptr, u32 offset
case BPF_DYNPTR_TYPE_RINGBUF: case BPF_DYNPTR_TYPE_RINGBUF:
return ptr->data + ptr->offset + offset; return ptr->data + ptr->offset + offset;
case BPF_DYNPTR_TYPE_SKB: case BPF_DYNPTR_TYPE_SKB:
return skb_header_pointer(ptr->data, ptr->offset + offset, len, buffer__opt); 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: case BPF_DYNPTR_TYPE_XDP:
{ {
void *xdp_ptr = bpf_xdp_pointer(ptr->data, ptr->offset + offset, len); void *xdp_ptr = bpf_xdp_pointer(ptr->data, ptr->offset + offset, len);