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Subject: Re: [PATCH] ath10k: htt_rx: Fix signedness bug in
 ath10k_update_per_peer_tx_stats
From:   "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To:     Ben Greear <greearb@candelatech.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        "David S. Miller" <davem@davemloft.net>
Cc:     ath10k@lists.infradead.org, linux-wireless@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
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Message-ID: <fcc51fdd-fc31-9d2c-2e68-4ceecbb86129@embeddedor.com>
Date:   Fri, 5 Oct 2018 21:15:49 +0200
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On 10/5/18 9:14 PM, Gustavo A. R. Silva wrote:
> 
> 
> On 10/5/18 9:09 PM, Ben Greear wrote:
>> On 10/05/2018 11:42 AM, Gustavo A. R. Silva wrote:
>>> Currently, the error handling for the call to function
>>> ath10k_get_legacy_rate_idx() doesn't work because
>>> *rate_idx* is of type u8 (8 bits, unsigned), which
>>> makes it impossible for it to hold a value less
>>> than 0.
>>>
>>> Fix this by changing the type of variable *rate_idx*
>>> to s8 (8 bits, signed).
>>
>> There are more than 127 rates, are you sure this is doing
>> what you want?
>>
> 
> Based on the following function, rate_idx can only hold values from 0 to 11
> 

... and of course -EINVAL too

> static inline int ath10k_get_legacy_rate_idx(struct ath10k *ar, u8 rate)
> {
>         static const u8 legacy_rates[] = {1, 2, 5, 11, 6, 9, 12,
>                                           18, 24, 36, 48, 54};
>         int i;
> 
>         for (i = 0; i < ARRAY_SIZE(legacy_rates); i++) {
>                 if (rate == legacy_rates[i])
>                         return i;
>         }
> 
>         ath10k_warn(ar, "Invalid legacy rate %hhd peer stats", rate);
>         return -EINVAL;
> }
> 
> Thanks
> --
> Gustavo
> 
>> Thanks,
>> Ben
>>
>>>
>>> Addresses-Coverity-ID: 1473914 ("Unsigned compared against 0")
>>> Fixes: 0189dbd71cbd ("ath10k: get the legacy rate index to update the txrate table")
>>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
>>> ---
>>> ?drivers/net/wireless/ath/ath10k/htt_rx.c | 3 ++-
>>> ?1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/net/wireless/ath/ath10k/htt_rx.c b/drivers/net/wireless/ath/ath10k/htt_rx.c
>>> index f240525..edd0e74 100644
>>> --- a/drivers/net/wireless/ath/ath10k/htt_rx.c
>>> +++ b/drivers/net/wireless/ath/ath10k/htt_rx.c
>>> @@ -2753,7 +2753,8 @@ ath10k_update_per_peer_tx_stats(struct ath10k *ar,
>>> ???????????????? struct ath10k_per_peer_tx_stats *peer_stats)
>>> ?{
>>> ???? struct ath10k_sta *arsta = (struct ath10k_sta *)sta->drv_priv;
>>> -??? u8 rate = 0, rate_idx = 0, sgi;
>>> +??? u8 rate = 0, sgi;
>>> +??? s8 rate_idx = 0;
>>> ???? struct rate_info txrate;
>>>
>>> ???? lockdep_assert_held(&ar->data_lock);
>>>
>>
>>