[PATCH v2] mwl8k: Use named struct for memcpy() region

[PATCH v2] mwl8k: Use named struct for memcpy() region

[Kees Cook]

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 named struct in struct mwl8k_cmd_set_key around members key_material,
tkip_tx_mic_key, and tkip_rx_mic_key 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 key_material.

"pahole" shows no size nor member offset changes to struct
mwl8k_cmd_set_key. "objdump -d" shows no object code changes.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
v1->v2: fixed wide indent, also not actually using struct_group
---
 drivers/net/wireless/marvell/mwl8k.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/marvell/mwl8k.c b/drivers/net/wireless/marvell/mwl8k.c
index 529e325498cd..864a2ba9efee 100644
--- a/drivers/net/wireless/marvell/mwl8k.c
+++ b/drivers/net/wireless/marvell/mwl8k.c
@@ -4225,9 +4225,11 @@ struct mwl8k_cmd_set_key {
 	__le32 key_info;
 	__le32 key_id;
 	__le16 key_len;
-	__u8 key_material[MAX_ENCR_KEY_LENGTH];
-	__u8 tkip_tx_mic_key[MIC_KEY_LENGTH];
-	__u8 tkip_rx_mic_key[MIC_KEY_LENGTH];
+	struct {
+		__u8 key_material[MAX_ENCR_KEY_LENGTH];
+		__u8 tkip_tx_mic_key[MIC_KEY_LENGTH];
+		__u8 tkip_rx_mic_key[MIC_KEY_LENGTH];
+	} tkip;
 	__le16 tkip_rsc_low;
 	__le32 tkip_rsc_high;
 	__le16 tkip_tsc_low;
@@ -4375,7 +4377,7 @@ static int mwl8k_cmd_encryption_set_key(struct ieee80211_hw *hw,
 		goto done;
 	}
 
-	memcpy(cmd->key_material, key->key, keymlen);
+	memcpy(&cmd->tkip, key->key, keymlen);
 	cmd->action = cpu_to_le32(action);
 
 	rc = mwl8k_post_pervif_cmd(hw, vif, &cmd->header);
-- 
2.30.2

Re: [PATCH v2] mwl8k: Use named struct for memcpy() region

[Kalle Valo]

Kees Cook <keescook@chromium.org> wrote:

> 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 named struct in struct mwl8k_cmd_set_key around members key_material,
> tkip_tx_mic_key, and tkip_rx_mic_key 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 key_material.
> 
> "pahole" shows no size nor member offset changes to struct
> mwl8k_cmd_set_key. "objdump -d" shows no object code changes.
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>

Patch applied to wireless-drivers-next.git, thanks.

f01b3774309f mwl8k: Use named struct for memcpy() region

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20211119004905.2348143-1-keescook@chromium.org/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches