On 3-1-2017 9:38, 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.
>
> Fix this by detecting unexpected channel and ignoring it.
>
> Fixes: 58de92d2f95e ("brcmfmac: use static superset of channels for wiphy bands")
> Signed-off-by: Rafał Miłecki <rafal@xxxxxxxxxx>
> ---
> I'm not sure what kind of material it is. It fixes possible memory corruption
> (serious thing?) but this bug was there since Apr 2015, so is it worth fixing
> in 4.10? Or maybe I should even cc stable?
> I don't think any released firmware reports any unexpected channel, so I guess
> noone ever hit this problem. I just noticed this possible problem when working
> on another feature.
Looking at the change I was going to ask if you actually hit the issue
you are addressing here. The channels in __wl_2ghz_channels and
__wl_5ghz_channels are complete list of channels for the particular band
so it would mean firmware behaves out-of-spec or firmware api was
changed. For robustness a change is acceptable I guess.
My general policy is to submit fixes to wireless-drivers (and stable)
only if it resolves a critical issue found during testing or a reported
issue.
> ---
> .../broadcom/brcm80211/brcmfmac/cfg80211.c | 29 +++++++++++-----------
> 1 file changed, 14 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> index 13ca3eb..0babfc7 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 +5872,33 @@ 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;
> }
> }
You could have kept the index construct and simply check if j ==
band->n_channels here to determine something is wrong.
> - channel[index].center_freq =
> - ieee80211_channel_to_frequency(ch.control_ch_num,
> - band->band);
> - channel[index].hw_value = ch.control_ch_num;
So you are also removing these assignments which indeed seem redundant.
Maybe make note of that in the commit message?
> + if (!channel) {
> + brcmf_err("Firmware reported unexpected channel %d\n",
> + ch.control_ch_num);
> + continue;
> + }
As stated above something is really off when this happens so should we
continue and try to make sense of what firmware provides or simply fail.
Regards,
Arend
