linux-kernel - Re: [PATCH] Prevent out-of-bounds read/write in bcmasp_netfilt_rd and bcmasp_netfilt

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Message-ID: <e3ac58b2-bb78-4364-94c0-f18c376ac132@broadcom.com>
Date:   Fri, 3 Nov 2023 11:23:16 -0700
From:   Justin Chen <justin.chen@...adcom.com>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Yuran Pereira <yuran.pereira@...mail.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        florian.fainelli@...adcom.com, linux-kernel@...r.kernel.org,
        edumazet@...gle.com, bcm-kernel-feedback-list@...adcom.com,
        kuba@...nel.org, pabeni@...hat.com,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] Prevent out-of-bounds read/write in bcmasp_netfilt_rd and
 bcmasp_netfilt_wr



On 11/3/23 5:57 AM, Greg KH wrote:
> On Fri, Nov 03, 2023 at 05:57:48PM +0530, Yuran Pereira wrote:
>> The functions `bcmasp_netfilt_rd` and `bcmasp_netfilt_wr` both call
>> `bcmasp_netfilt_get_reg_offset` which, when it fails, returns `-EINVAL`.
>> This could lead to an out-of-bounds read or write when `rx_filter_core_rl`
>> or `rx_filter_core_wl` is called.
>>
>> This patch adds a check in both functions to return immediately if
>> `bcmasp_netfilt_get_reg_offset` fails. This prevents potential out-of-bounds read
>> or writes, and ensures that no undefined or buggy behavior would originate from
>> the failure of `bcmasp_netfilt_get_reg_offset`.
>>
>> Addresses-Coverity-IDs: 1544536 ("Out-of-bounds access")
>> Signed-off-by: Yuran Pereira <yuran.pereira@...mail.com>
>> ---
>>   drivers/net/ethernet/broadcom/asp2/bcmasp.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/broadcom/asp2/bcmasp.c b/drivers/net/ethernet/broadcom/asp2/bcmasp.c
>> index 29b04a274d07..8b90b761bdec 100644
>> --- a/drivers/net/ethernet/broadcom/asp2/bcmasp.c
>> +++ b/drivers/net/ethernet/broadcom/asp2/bcmasp.c
>> @@ -227,6 +227,8 @@ static void bcmasp_netfilt_wr(struct bcmasp_priv *priv,
>>   
>>   	reg_offset = bcmasp_netfilt_get_reg_offset(priv, nfilt, reg_type,
>>   						   offset);
>> +	if (reg_offset < 0)
>> +		return;
>>   
>>   	rx_filter_core_wl(priv, val, reg_offset);
>>   }
>> @@ -244,6 +246,8 @@ static u32 bcmasp_netfilt_rd(struct bcmasp_priv *priv,
>>   
>>   	reg_offset = bcmasp_netfilt_get_reg_offset(priv, nfilt, reg_type,
>>   						   offset);
>> +	if (reg_offset < 0)
>> +		return 0;
> 
> Shouldn't you return an error here?
> 
> thanks
> 
> greg k-h

As long as offset is less than MAX_WAKE_FILTER_SIZE we don't need to 
worry about error checking. This is already checked before we call 
netfilt_get_reg_offset() in both cases. Instead of returning -EINVAL in 
neffilt_get_reg_offset() lets return 0. This will silence the coverity 
check. In practice we will never hit this logic.

Thanks,
Justin

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