Re: [PATCH 05/32] brcmfmac: Use mem_to_flex_dup() with struct brcmf_fweh_queue_item

[Arend van Spriel <arend.vanspriel@xxxxxxxxxxxx>]

On 5/4/2022 3:44 AM, Kees Cook wrote:
> As part of the work to perform bounds checking on all memcpy() uses,
> replace the open-coded a deserialization of bytes out of memory into a
> trailing flexible array by using a flex_array.h helper to perform the
> allocation, bounds checking, and copying.
Reviewed-by: Arend van Spriel <aspriel@xxxxxxxxx>
> Cc: Franky Lin <franky.lin@xxxxxxxxxxxx>
> Cc: Hante Meuleman <hante.meuleman@xxxxxxxxxxxx>
> Cc: Kalle Valo <kvalo@xxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: linux-wireless@xxxxxxxxxxxxxxx
> Cc: brcm80211-dev-list.pdl@xxxxxxxxxxxx
> Cc: SHA-cyfmac-dev-list@xxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>   .../net/wireless/broadcom/brcm80211/brcmfmac/fweh.c   | 11 ++++-------
>   1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c
> index bc3f4e4edcdf..bea798ca6466 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c
> @@ -32,8 +32,8 @@ struct brcmf_fweh_queue_item {
>   	u8 ifidx;
>   	u8 ifaddr[ETH_ALEN];
>   	struct brcmf_event_msg_be emsg;
> -	u32 datalen;
> -	u8 data[];
> +	DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(u32, datalen);
> +	DECLARE_FLEX_ARRAY_ELEMENTS(u8, data);
>   };
>   
>   /*
> @@ -395,7 +395,7 @@ void brcmf_fweh_process_event(struct brcmf_pub *drvr,
>   {
>   	enum brcmf_fweh_event_code code;
>   	struct brcmf_fweh_info *fweh = &drvr->fweh;
> -	struct brcmf_fweh_queue_item *event;
> +	struct brcmf_fweh_queue_item *event = NULL;
>   	void *data;
>   	u32 datalen;
>   
> @@ -414,8 +414,7 @@ void brcmf_fweh_process_event(struct brcmf_pub *drvr,
>   	    datalen + sizeof(*event_packet) > packet_len)
>   		return;
>   
> -	event = kzalloc(sizeof(*event) + datalen, gfp);
> -	if (!event)
> +	if (mem_to_flex_dup(&event, data, datalen, gfp))
>   		return;
>   
>   	event->code = code;
> @@ -423,8 +422,6 @@ void brcmf_fweh_process_event(struct brcmf_pub *drvr,
>   
>   	/* use memcpy to get aligned event message */
>   	memcpy(&event->emsg, &event_packet->msg, sizeof(event->emsg));
> -	memcpy(event->data, data, datalen);
> -	event->datalen = datalen;

So does mem_to_flex_dup() store event->datalen?

Don't have the entire thread so missing bits and pieces, but at least 
this raises questions for me.

Thanks,
Arend

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