Re: [PATCH] wifi: brcmfmac: Fix field-spanning write in brcmf_scan_params_v2_to_v1()

[Kees Cook <keescook@chromium.org>]

On Sat, Jul 29, 2023 at 04:05:00PM +0200, Hans de Goede wrote:
> Using brcmfmac with 6.5-rc3 on a brcmfmac43241b4-sdio triggers
> a backtrace caused by the following field-spanning error:
> 
> memcpy: detected field-spanning write (size 120) of single field
>   "&params_le->channel_list[0]" at
>   drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c:1072 (size 2)
> 
> Fix this by replacing the channel_list[1] declaration at the end of
> the struct with a flexible array declaration.
> 
> Most users of struct brcmf_scan_params_le calculate the size to alloc
> using the size of the non flex-array part of the struct + needed extra
> space, so they do not care about sizeof(struct brcmf_scan_params_le).
> 
> brcmf_notify_escan_complete() however uses the struct on the stack,
> expecting there to be room for at least 1 entry in the channel-list
> to store the special -1 abort channel-id.
> 
> To make this work use an anonymous union with a padding member
> added + the actual channel_list flexible array.
> 
> Cc: Kees Cook <keescook@chromium.org>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Looks good to me; it's consistent with how similar 1-element arrays
with sensitive structure sizes have been updated lately. Thanks for
the investigation!

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

-- 
Kees Cook