[PATCH] staging: r8188eu: Fix PPPoE tag insertion on big endian systems

[PATCH] staging: r8188eu: Fix PPPoE tag insertion on big endian systems

[Guenter Roeck]

In __nat25_add_pppoe_tag(), the tag length is read from the tag data
structure. The value is kept in network format, but read as raw value.
With -Warray-bounds, this results in the following gcc error/warning
when building the driver on a big endian system such as alpha.

In function '__nat25_add_pppoe_tag',
    inlined from 'nat25_db_handle' at
	drivers/staging/r8188eu/core/rtw_br_ext.c:479:11:
arch/alpha/include/asm/string.h:22:16: error:
	'__builtin_memcpy' forming offset [40, 2051] is out of the bounds
	[0, 40] of object 'tag_buf' with type 'unsigned char[40]'

Add the missing ntohs().

Fixes: 15865124feed ("staging: r8188eu: introduce new core dir for RTL8188eu driver")
Cc: Phillip Potter <phil@philpotter.co.uk>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/staging/r8188eu/core/rtw_br_ext.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/r8188eu/core/rtw_br_ext.c b/drivers/staging/r8188eu/core/rtw_br_ext.c
index d68611ef22f8..31bcd495ec04 100644
--- a/drivers/staging/r8188eu/core/rtw_br_ext.c
+++ b/drivers/staging/r8188eu/core/rtw_br_ext.c
@@ -70,7 +70,7 @@ static int __nat25_add_pppoe_tag(struct sk_buff *skb, struct pppoe_tag *tag)
 	struct pppoe_hdr *ph = (struct pppoe_hdr *)(skb->data + ETH_HLEN);
 	int data_len;
 
-	data_len = tag->tag_len + TAG_HDR_LEN;
+	data_len = htons(tag->tag_len) + TAG_HDR_LEN;
 	if (skb_tailroom(skb) < data_len)
 		return -1;
 
-- 
2.35.1

Re: [PATCH] staging: r8188eu: Fix PPPoE tag insertion on big endian systems

[Larry Finger]

On 4/1/22 10:12, Guenter Roeck wrote:
> In __nat25_add_pppoe_tag(), the tag length is read from the tag data
> structure. The value is kept in network format, but read as raw value.
> With -Warray-bounds, this results in the following gcc error/warning
> when building the driver on a big endian system such as alpha.
> 
> In function '__nat25_add_pppoe_tag',
>      inlined from 'nat25_db_handle' at
> 	drivers/staging/r8188eu/core/rtw_br_ext.c:479:11:
> arch/alpha/include/asm/string.h:22:16: error:
> 	'__builtin_memcpy' forming offset [40, 2051] is out of the bounds
> 	[0, 40] of object 'tag_buf' with type 'unsigned char[40]'
> 
> Add the missing ntohs().
> 
> Fixes: 15865124feed ("staging: r8188eu: introduce new core dir for RTL8188eu driver")
> Cc: Phillip Potter <phil@philpotter.co.uk>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
>   drivers/staging/r8188eu/core/rtw_br_ext.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/r8188eu/core/rtw_br_ext.c b/drivers/staging/r8188eu/core/rtw_br_ext.c
> index d68611ef22f8..31bcd495ec04 100644
> --- a/drivers/staging/r8188eu/core/rtw_br_ext.c
> +++ b/drivers/staging/r8188eu/core/rtw_br_ext.c
> @@ -70,7 +70,7 @@ static int __nat25_add_pppoe_tag(struct sk_buff *skb, struct pppoe_tag *tag)
>   	struct pppoe_hdr *ph = (struct pppoe_hdr *)(skb->data + ETH_HLEN);
>   	int data_len;
>   
> -	data_len = tag->tag_len + TAG_HDR_LEN;
> +	data_len = htons(tag->tag_len) + TAG_HDR_LEN;
>   	if (skb_tailroom(skb) < data_len)
>   		return -1;
>   

Strange that a BE compiler would generate a warning for what is actually an 
execution error on LE platforms.

I prefer be16_to_cpu() to htons() as the former makes it clearer what is 
happening, but I suppose that is a matter of choice.

Reviewed_by: Larry Finger <Larry.Finger@lwfinger.net>

Incidentally, Sparse shows 3 more __be16 problems in this routine. I leave their 
fixing to you.

Larry

Re: [PATCH] staging: r8188eu: Fix PPPoE tag insertion on big endian systems

[Guenter Roeck]

On 4/1/22 11:40, Larry Finger wrote:
> On 4/1/22 10:12, Guenter Roeck wrote:
>> In __nat25_add_pppoe_tag(), the tag length is read from the tag data
>> structure. The value is kept in network format, but read as raw value.
>> With -Warray-bounds, this results in the following gcc error/warning
>> when building the driver on a big endian system such as alpha.
>>
>> In function '__nat25_add_pppoe_tag',
>>      inlined from 'nat25_db_handle' at
>>     drivers/staging/r8188eu/core/rtw_br_ext.c:479:11:
>> arch/alpha/include/asm/string.h:22:16: error:
>>     '__builtin_memcpy' forming offset [40, 2051] is out of the bounds
>>     [0, 40] of object 'tag_buf' with type 'unsigned char[40]'
>>
>> Add the missing ntohs().
>>
>> Fixes: 15865124feed ("staging: r8188eu: introduce new core dir for RTL8188eu driver")
>> Cc: Phillip Potter <phil@philpotter.co.uk>
>> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>> ---
>>   drivers/staging/r8188eu/core/rtw_br_ext.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/staging/r8188eu/core/rtw_br_ext.c b/drivers/staging/r8188eu/core/rtw_br_ext.c
>> index d68611ef22f8..31bcd495ec04 100644
>> --- a/drivers/staging/r8188eu/core/rtw_br_ext.c
>> +++ b/drivers/staging/r8188eu/core/rtw_br_ext.c
>> @@ -70,7 +70,7 @@ static int __nat25_add_pppoe_tag(struct sk_buff *skb, struct pppoe_tag *tag)
>>       struct pppoe_hdr *ph = (struct pppoe_hdr *)(skb->data + ETH_HLEN);
>>       int data_len;
>> -    data_len = tag->tag_len + TAG_HDR_LEN;
>> +    data_len = htons(tag->tag_len) + TAG_HDR_LEN;

Wonder where my brain was. That should have been ntohs().

>>       if (skb_tailroom(skb) < data_len)
>>           return -1;
> 
> Strange that a BE compiler would generate a warning for what is actually an execution error on LE platforms.
> 
> I prefer be16_to_cpu() to htons() as the former makes it clearer what is happening, but I suppose that is a matter of choice.
> 
The rest of the code uses htons/ntohs, so I prefer to follow that lead.

> Reviewed_by: Larry Finger <Larry.Finger@lwfinger.net>
> 
> Incidentally, Sparse shows 3 more __be16 problems in this routine. I leave their fixing to you.
> 

I'll need to resend anyway, so I'll track those down and fix them as well.

Thanks,
Guenter

Re: [PATCH] staging: r8188eu: Fix PPPoE tag insertion on big endian systems

[Larry Finger]

On 4/1/22 14:25, Guenter Roeck wrote:
> The rest of the code uses htons/ntohs, so I prefer to follow that lead.

You just proved my point. It is hard to get be16_to_cpu() wrong. Sparse will 
flag the error when you use cpu_to_be16() instead. I expect that your 
htons/ntohs problem would also have shown up with Sparse.

Larry

Re: [PATCH] staging: r8188eu: Fix PPPoE tag insertion on big endian systems

[Guenter Roeck]

On 4/1/22 13:25, Larry Finger wrote:
> On 4/1/22 14:25, Guenter Roeck wrote:
>> The rest of the code uses htons/ntohs, so I prefer to follow that lead.
> 
> You just proved my point. It is hard to get be16_to_cpu() wrong. Sparse will flag the error when you use cpu_to_be16() instead. I expect that your htons/ntohs problem would also have shown up with Sparse.
> 

Ok, you made your point. I'll use be16_to_cpu() - the driver
already uses it elsewhere anyway. As for the other problems,
I am not sure if the driver ever worked. The function we are
looking at can't really have worked on a little endian system
because of the missing conversion, and the same is true for the
other code flagged by sparse. I think I'll just add a note
to this patch and let the driver authors decide what to do
about those problems.

Guenter

Re: [PATCH] staging: r8188eu: Fix PPPoE tag insertion on big endian systems

[Dan Carpenter]

On Sat, Apr 02, 2022 at 02:18:22PM -0700, Guenter Roeck wrote:
> On 4/1/22 13:25, Larry Finger wrote:
> > On 4/1/22 14:25, Guenter Roeck wrote:
> > > The rest of the code uses htons/ntohs, so I prefer to follow that lead.
> > 
> > You just proved my point. It is hard to get be16_to_cpu() wrong. Sparse will flag the error when you use cpu_to_be16() instead. I expect that your htons/ntohs problem would also have shown up with Sparse.
> > 
> 
> Ok, you made your point. I'll use be16_to_cpu() - the driver
> already uses it elsewhere anyway. As for the other problems,
> I am not sure if the driver ever worked. The function we are
> looking at can't really have worked on a little endian system
> because of the missing conversion, and the same is true for the
> other code flagged by sparse. I think I'll just add a note
> to this patch and let the driver authors decide what to do
> about those problems.
> 
> Guenter

This is already fixed along with a couple related bugs in commit
2d959a842a8f ("staging: r8188eu: Fix sparse endianness warnings.").

https://lore.kernel.org/r/YkPK/QmLAp3BkygY@sckzor-linux.localdomain

It's in staging-next but hasn't hit linux-next yet.

regards,
dan carpenter

Re: [PATCH] staging: r8188eu: Fix PPPoE tag insertion on big endian systems

[Guenter Roeck]

On 4/4/22 02:53, Dan Carpenter wrote:
> On Sat, Apr 02, 2022 at 02:18:22PM -0700, Guenter Roeck wrote:
>> On 4/1/22 13:25, Larry Finger wrote:
>>> On 4/1/22 14:25, Guenter Roeck wrote:
>>>> The rest of the code uses htons/ntohs, so I prefer to follow that lead.
>>>
>>> You just proved my point. It is hard to get be16_to_cpu() wrong. Sparse will flag the error when you use cpu_to_be16() instead. I expect that your htons/ntohs problem would also have shown up with Sparse.
>>>
>>
>> Ok, you made your point. I'll use be16_to_cpu() - the driver
>> already uses it elsewhere anyway. As for the other problems,
>> I am not sure if the driver ever worked. The function we are
>> looking at can't really have worked on a little endian system
>> because of the missing conversion, and the same is true for the
>> other code flagged by sparse. I think I'll just add a note
>> to this patch and let the driver authors decide what to do
>> about those problems.
>>
>> Guenter
> 
> This is already fixed along with a couple related bugs in commit
> 2d959a842a8f ("staging: r8188eu: Fix sparse endianness warnings.").
> 
> https://lore.kernel.org/r/YkPK/QmLAp3BkygY@sckzor-linux.localdomain
> 
> It's in staging-next but hasn't hit linux-next yet.
> 

Good to hear. Too bad I got it a minute too late - I just sent v3.

Guenter