Similarly to the previous patch fixing the flow_dissector ctx accesses,
nf_is_valid_access also doesn't check that ctx accesses are aligned.
Contrary to flow_dissector programs, netfilter programs don't have
context conversion. The unaligned ctx accesses are therefore allowed by
the verifier.
Fixes: fd9c663b9ad6 ("bpf: minimal support for programs hooked into netfilter framework")
Signed-off-by: Paul Chaignon <paul.chaignon@xxxxxxxxx>
---
net/netfilter/nf_bpf_link.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/netfilter/nf_bpf_link.c b/net/netfilter/nf_bpf_link.c
index 3e4fb9ddcd36..46e667a50d98 100644
--- a/net/netfilter/nf_bpf_link.c
+++ b/net/netfilter/nf_bpf_link.c
@@ -296,6 +296,9 @@ static bool nf_is_valid_access(int off, int size, enum bpf_access_type type,
if (off < 0 || off >= sizeof(struct bpf_nf_ctx))
return false;
+ if (off % size != 0)
+ return false;
+
if (type == BPF_WRITE)
return false;
--
2.43.0
