On 3-1-2017 17:49, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal@xxxxxxxxxx>
>
> Our code was assigning number of channels to the index variable by
> default. If firmware reported channel we didn't predict this would
> result in using that initial index value and writing out of array. This
> never happened so far (we got a complete list of supported channels) but
> it means possible memory corruption so we should handle it anyway.
>
> This patch simply detects unexpected channel and ignores it.
>
> As we don't try to create new entry now, it's also safe to drop hw_value
> and center_freq assignment. For known channels we have these set anyway.
>
> I decided to fix this issue by assigning NULL or a target channel to the
> channel variable. This was one of possible ways, I prefefred this one as
> it also avoids using channel[index] over and over.
>
> Fixes: 58de92d2f95e ("brcmfmac: use static superset of channels for wiphy bands")
> Signed-off-by: Rafał Miłecki <rafal@xxxxxxxxxx>
> ---
> V2: Add extra comment in code for not-found channel.
> Make it clear this problem have never been seen so far
> Explain why it's safe to drop extra assignments
> Note & reason changing channel variable usage
> ---
> .../broadcom/brcm80211/brcmfmac/cfg80211.c | 32 ++++++++++++----------
> 1 file changed, 17 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> index 9c2c128..a16dd7b 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> @@ -5825,7 +5825,6 @@ static int brcmf_construct_chaninfo(struct brcmf_cfg80211_info *cfg,
> u32 i, j;
> u32 total;
> u32 chaninfo;
> - u32 index;
>
> pbuf = kzalloc(BRCMF_DCMD_MEDLEN, GFP_KERNEL);
>
> @@ -5873,33 +5872,36 @@ static int brcmf_construct_chaninfo(struct brcmf_cfg80211_info *cfg,
> ch.bw == BRCMU_CHAN_BW_80)
> continue;
>
> - channel = band->channels;
> - index = band->n_channels;
> + channel = NULL;
> for (j = 0; j < band->n_channels; j++) {
> - if (channel[j].hw_value == ch.control_ch_num) {
> - index = j;
> + if (band->channels[j].hw_value == ch.control_ch_num) {
> + channel = &band->channels[j];
> break;
> }
> }
> - channel[index].center_freq =
> - ieee80211_channel_to_frequency(ch.control_ch_num,
> - band->band);
> - channel[index].hw_value = ch.control_ch_num;
> + if (!channel) {
> + /* It seems firmware supports some channel we never
> + * considered. Something new in IEEE standard?
> + */
> + brcmf_err("Firmware reported unexpected channel %d\n",
> + ch.control_ch_num);
Maybe rephrase to "Ignoring unexpected firmware channel %d\n" so
end-users are not alarmed by this error message. I think using
brcmf_err() is justified, but you may even consider chiming down to
brcmf_dbg(INFO, ...).
Regards,
Arend
