linux-kernel - Re: [PATCH] qed: fix uninit pointer read in qed_mcp_nvm_info

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Message-ID: <4c8a6841-06d1-4bc0-8470-380448006036@gmail.com>
Date: Sun, 15 Dec 2024 02:11:42 +0100
From: Gianfranco Trad <gianf.trad@...il.com>
To: Simon Horman <horms@...nel.org>
Cc: manishc@...vell.com, andrew+netdev@...n.ch, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 skhan@...uxfoundation.org
Subject: Re: [PATCH] qed: fix uninit pointer read in
 qed_mcp_nvm_info_populate()

On 13/12/24 14:31, Simon Horman wrote:
> On Fri, Dec 13, 2024 at 01:13:12PM +0100, Gianfranco Trad wrote:
>> On 12/12/24 18:04, Simon Horman wrote:
>>> On Wed, Dec 11, 2024 at 02:40:42PM +0100, Gianfranco Trad wrote:
>>>> Coverity reports an uninit pointer read in qed_mcp_nvm_info_populate().
>>>> If qed_mcp_bist_nvm_get_num_images() returns -EOPNOTSUPP, this leads to
>>>> jump to label out with nvm_info.image_att being uninit while assigning it
>>>> to p_hwfn->nvm_info.image_att.
>>>> Add check on rc against -EOPNOTSUPP to avoid such uninit pointer read.
>>>>
>>>> Closes: https://scan5.scan.coverity.com/#/project-view/63204/10063?selectedIssue=1636666
>>>> Signed-off-by: Gianfranco Trad <gianf.trad@...il.com>
>>>> ---
>>>> Note:
>>>> - Fixes: tag should be "7a0ea70da56e net/qed: allow old cards not supporting "num_images" to work" ?
>>>>    drivers/net/ethernet/qlogic/qed/qed_mcp.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/net/ethernet/qlogic/qed/qed_mcp.c b/drivers/net/ethernet/qlogic/qed/qed_mcp.c
>>>> index b45efc272fdb..127943b39f61 100644
>>>> --- a/drivers/net/ethernet/qlogic/qed/qed_mcp.c
>>>> +++ b/drivers/net/ethernet/qlogic/qed/qed_mcp.c
>>>> @@ -3387,7 +3387,7 @@ int qed_mcp_nvm_info_populate(struct qed_hwfn *p_hwfn)
>>>>    	}
>>>>    out:
>>>>    	/* Update hwfn's nvm_info */
>>>> -	if (nvm_info.num_images) {
>>>> +	if (nvm_info.num_images && rc != -EOPNOTSUPP) {
>>>>    		p_hwfn->nvm_info.num_images = nvm_info.num_images;
>>>>    		kfree(p_hwfn->nvm_info.image_att);
>>>>    		p_hwfn->nvm_info.image_att = nvm_info.image_att;
>>>
>>
>> Hi Simon,
>>
>>> Are you sure that nvm_info.num_images can be non-zero if rc == -EOPNOTSUPP?
>>>
>>
>> In the coverity report, the static analyzer is able to take the true branch
>> on nvm_info.num_images. I didn't physically reproduce this logical state as
>> I don't possess the matching hardware.
>>
>>> The cited commit state:
>>>
>>>       Commit 43645ce03e00 ("qed: Populate nvm image attribute shadow.")
>>>       added support for populating flash image attributes, notably
>>>       "num_images". However, some cards were not able to return this
>>>       information. In such cases, the driver would return EINVAL, causing the
>>>       driver to exit.
>>>
>>>       Add check to return EOPNOTSUPP instead of EINVAL when the card is not
>>>       able to return these information. The caller function already handles
>>>       EOPNOTSUPP without error.
>>>
>>> So I would expect that nvm_info.num_images is 0.
>>>
>>> If not, perhaps an alternate fix is to make that so, either by setting
>>> it in qed_mcp_bist_nvm_get_num_images, or where the return value of
>>> qed_mcp_bist_nvm_get_num_images is checked (just before the goto out).
>>>
>>
>> Makes sense, so something like this I suppose:
>>
>> --- a/drivers/net/ethernet/qlogic/qed/qed_mcp.c
>> +++ b/drivers/net/ethernet/qlogic/qed/qed_mcp.c
>> @@ -3301,8 +3301,10 @@ int qed_mcp_bist_nvm_get_num_images(struct qed_hwfn
>> *p_hwfn,
>>    	if (rc)
>>    		return rc;
>>
>> -	if (((rsp & FW_MSG_CODE_MASK) == FW_MSG_CODE_UNSUPPORTED))
>> +	if (((rsp & FW_MSG_CODE_MASK) == FW_MSG_CODE_UNSUPPORTED)) {
>> +		*num_images = 0;
>>    		rc = -EOPNOTSUPP;
>> +	}
>>
>> Or the second option you stated.
> 
> Yes, that is what I was thinking.
> But as it is a side effect, and thus hidden slightly,
> on reflection perhaps the second option is better. IDK.
> 

Got it. Will send a v2 accordingly.

Thanks for your time,
--Gian

>>> And, in any case I think some testing is in order.
>>
>> I strongly agree. Let me know if I can help more with this.
>>
>> Thanks for your time,
>> --Gian
>>