wifi: brcmfmac: fweh: Add __counted_by for struct brcmf_fweh_queue_item and use struc...

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

Also, relocate `event->datalen = datalen;` to before calling
`memcpy(event->data, data, datalen);`, so that the __counted_by
annotation has effect, and flex-array member `data` can be properly
bounds-checked at run-time.

While there, use struct_size() helper, instead of the open-coded
version, to calculate the size for the allocation of the whole
flexible structure, including of course, the flexible-array member.

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

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/ZSRzrIe0345eymk2@work

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c
index dac7eb77799bd158d8e4d6e487a236e3784a8cfa..68960ae98987134cb2f87c505320021eea7fd96e 100644 (file)
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c
@@ -33,7 +33,7 @@ struct brcmf_fweh_queue_item {
        u8 ifaddr[ETH_ALEN];
        struct brcmf_event_msg_be emsg;
        u32 datalen;
-       u8 data[];
+       u8 data[] __counted_by(datalen);
 };
 
 /*
@@ -418,17 +418,17 @@ void brcmf_fweh_process_event(struct brcmf_pub *drvr,
            datalen + sizeof(*event_packet) > packet_len)
                return;
 
-       event = kzalloc(sizeof(*event) + datalen, gfp);
+       event = kzalloc(struct_size(event, data, datalen), gfp);
        if (!event)
                return;
 
+       event->datalen = datalen;
        event->code = code;
        event->ifidx = event_packet->msg.ifidx;
 
        /* use memcpy to get aligned event message */
        memcpy(&event->emsg, &event_packet->msg, sizeof(event->emsg));
        memcpy(event->data, data, datalen);
-       event->datalen = datalen;
        memcpy(event->ifaddr, event_packet->eth.h_dest, ETH_ALEN);
 
        brcmf_fweh_queue_event(fweh, event);