[PATCH 18/64] cxgb3: Use struct_group() for memcpy() region

Kees Cook
2021-07-27T20:59:42Z

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), memmove(), and memset(), avoid
intentionally writing across neighboring fields.

Use struct_group() in struct rss_hdr around members imm_data and intr_gen,
so they can be referenced together. This will allow memcpy() and sizeof()
to more easily reason about sizes, improve readability, and avoid future
warnings about writing beyond the end of imm_data.

"pahole" shows no size nor member offset changes to struct rss_hdr.
"objdump -d" shows no object code changes.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/net/ethernet/chelsio/cxgb3/sge.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/chelsio/cxgb3/sge.c b/drivers/net/ethernet/chelsio/cxgb3/sge.c
index cb5c79c43bc9..1ab1bd86a3a6 100644
--- a/drivers/net/ethernet/chelsio/cxgb3/sge.c
+++ b/drivers/net/ethernet/chelsio/cxgb3/sge.c
@@ -126,8 +126,10 @@ struct rsp_desc { /* response queue descriptor */
struct rss_header rss_hdr;
__be32 flags;
__be32 len_cq;
- u8 imm_data[47];
- u8 intr_gen;
+ struct_group(immediate,
+ u8 imm_data[47];
+ u8 intr_gen;
+ );
};

/*
@@ -929,7 +931,8 @@ static inline struct sk_buff *get_imm_packet(const struct rsp_desc *resp)

if (skb) {
__skb_put(skb, IMMED_PKT_SIZE);
- skb_copy_to_linear_data(skb, resp->imm_data, IMMED_PKT_SIZE);
+ BUILD_BUG_ON(IMMED_PKT_SIZE != sizeof(resp->immediate));
+ skb_copy_to_linear_data(skb, &resp->immediate, IMMED_PKT_SIZE);
}
return skb;
}
--
2.30.2