staging: r8188eu: Fix PPPoE tag insertion on big endian systems

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 <[email protected]>

Signed-off-by Guenter Roeck <[email protected]>

---
  drivers/staging/r8188eu/core/rtw_br_ext.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

drivers/staging/r8188eu/core/rtw_br_ext.c +0 -0

index d68611ef22f8..31bcd495ec04 100644

Quoted 21 lines · 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 <[email protected]>

Signed-off-by Guenter Roeck <[email protected]>

---
  drivers/staging/r8188eu/core/rtw_br_ext.c | 2 +-

  1 file changed, 1 insertion(+), 1 deletion(-)

drivers/staging/r8188eu/core/rtw_br_ext.c static int __nat25_add_pppoe_tag(struct sk_buff *skb, struct pppoe_tag *tag) · line 72

Quoted 9 lines

drivers/staging/r8188eu/core/rtw_br_ext.c +1 -1

index d68611ef22f8..31bcd495ec04 100644
@@ -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;

drivers/staging/r8188eu/core/rtw_br_ext.c static int __nat25_add_pppoe_tag(struct sk_buff *skb, struct pppoe_tag *tag) · line 75

Quoted 2 lines

drivers/staging/r8188eu/core/rtw_br_ext.c +0 -0

       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 <[email protected]>

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

The rest of the code uses htons/ntohs, so I prefer to follow that lead.

Quoted 1 line · Guenter Roeck

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.

Quoted 5 lines · Larry Finger

Quoted 1 line · Guenter Roeck

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

Quoted 16 lines · Guenter Roeck

Quoted 5 lines · Larry Finger

Quoted 1 line · Guenter Roeck

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.

Quoted 1 line

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/[email protected]

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