On Mon, May 16, 2022 at 02:49:21PM +0200, Arend van Spriel wrote:

On 5/4/2022 3:44 AM, Kees Cook wrote:

quoted

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 <redacted>

Thanks!

quoted

[...]

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);
  };

[...]

@@ -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.

Yes, that's part of the internal workings here -- the flex array counter
is declared and will be set as part of the copy.

-- 
Kees Cook