There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].

This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().

This issue was found with the help of Coccinelle and audited and fixed,
manually.

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/79
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 .../net/wireless/broadcom/brcm80211/brcmfmac/p2p.c   | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
index 4735063e4c03..d3f08d4f380b 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
@@ -158,7 +158,7 @@ struct brcmf_p2p_pub_act_frame {
 	u8	oui_type;
 	u8	subtype;
 	u8	dialog_token;
-	u8	elts[1];
+	u8	elts[];
 };
 
 /**
@@ -177,7 +177,7 @@ struct brcmf_p2p_action_frame {
 	u8	type;
 	u8	subtype;
 	u8	dialog_token;
-	u8	elts[1];
+	u8	elts[];
 };
 
 /**
@@ -192,7 +192,7 @@ struct brcmf_p2psd_gas_pub_act_frame {
 	u8	category;
 	u8	action;
 	u8	dialog_token;
-	u8	query_data[1];
+	u8	query_data[];
 };
 
 /**
@@ -225,7 +225,7 @@ static bool brcmf_p2p_is_pub_action(void *frame, u32 frame_len)
 		return false;
 
 	pact_frm = (struct brcmf_p2p_pub_act_frame *)frame;
-	if (frame_len < sizeof(struct brcmf_p2p_pub_act_frame) - 1)
+	if (frame_len < sizeof(*pact_frm))
 		return false;
 
 	if (pact_frm->category == P2P_PUB_AF_CATEGORY &&
@@ -253,7 +253,7 @@ static bool brcmf_p2p_is_p2p_action(void *frame, u32 frame_len)
 		return false;
 
 	act_frm = (struct brcmf_p2p_action_frame *)frame;
-	if (frame_len < sizeof(struct brcmf_p2p_action_frame) - 1)
+	if (frame_len < sizeof(*act_frm))
 		return false;
 
 	if (act_frm->category == P2P_AF_CATEGORY &&
@@ -280,7 +280,7 @@ static bool brcmf_p2p_is_gas_action(void *frame, u32 frame_len)
 		return false;
 
 	sd_act_frm = (struct brcmf_p2psd_gas_pub_act_frame *)frame;
-	if (frame_len < sizeof(struct brcmf_p2psd_gas_pub_act_frame) - 1)
+	if (frame_len < sizeof(*sd_act_frm))
 		return false;
 
 	if (sd_act_frm->category != P2PSD_ACTION_CATEGORY)
-- 
2.27.0

"Gustavo A. R. Silva" <gustavoars@kernel.org> wrote:

> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
> 
> This helps with the ongoing efforts to globally enable -Warray-bounds
> and get us closer to being able to tighten the FORTIFY_SOURCE routines
> on memcpy().
> 
> This issue was found with the help of Coccinelle and audited and fixed,
> manually.
> 
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Link: https://github.com/KSPP/linux/issues/79
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Patch applied to wireless-next.git, thanks.

f3c04fffe271 brcmfmac: p2p: Replace one-element arrays with flexible-array members

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20220204232228.GA442895@embeddedor/

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