bpf: Return an error pointer for skb metadata when CONFIG_NET=n
Kernel Test Robot reported a compiler warning - a null pointer may be
passed to memmove in __bpf_dynptr_{read,write} when building without
networking support.
The warning is correct from a static analysis standpoint, but not actually
reachable. Without CONFIG_NET, creating dynptrs to skb metadata is
impossible since the constructor kfunc is missing.
Silence the false-postive diagnostic message by returning an error pointer
from bpf_skb_meta_pointer stub when CONFIG_NET=n.
Fixes: 6877cd392bae ("bpf: Enable read/write access to skb metadata through a dynptr")
Closes: https://lore.kernel.org/oe-kbuild-all/202508212031.ir9b3B6Q-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20250901-dynptr-skb-meta-no-net-v2-1-ce607fcb6091@cloudflare.com
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 9ed21b6..af6d935 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1822,7 +1822,7 @@ static inline void bpf_xdp_copy_buf(struct xdp_buff *xdp, unsigned long off, voi
static inline void *bpf_skb_meta_pointer(struct sk_buff *skb, u32 offset)
{
- return NULL;
+ return ERR_PTR(-EOPNOTSUPP);
}
#endif /* CONFIG_NET */
