From: Alexei Starovoitov <ast@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
include/linux/skbuff.h | 10 +++++++++-
kernel/bpf/helpers.c | 5 ++++-
2 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 91ed66952580..f276d0e9816f 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -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.
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 9e80efa59a5d..b8ab3bea71b7 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2239,7 +2239,10 @@ __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:
- 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:
{
void *xdp_ptr = bpf_xdp_pointer(ptr->data, ptr->offset + offset, len);
--
2.34.1
