Re: [PATCH] brcm80211: brcmfmac: Ensure that incoming skb's are writable

[James Hughes]

On 23 April 2017 at 20:34, Arend Van Spriel
 wrote:
> On 21-4-2017 11:22, James Hughes wrote:
>> On 20 April 2017 at 20:48, Arend van Spriel
>>  wrote:
>>> + linux-wireless
>>>
>>> On 4/20/2017 1:16 PM, James Hughes wrote:

 The driver was adding header information to incoming skb
 without ensuring the head was uncloned and hence writable.

 skb_cow_head has been used to ensure they are writable, however,
 this required some changes to error handling to ensure that
 if skb_cow_head failed it was not ignored.

 This really needs to be reviewed by someone who is more familiar
 with this code base to ensure any deallocation of skb's is
 still correct.

 Signed-off-by: James Hughes 
 ---
   .../wireless/broadcom/brcm80211/brcmfmac/bcdc.c| 15 --
   .../wireless/broadcom/brcm80211/brcmfmac/core.c| 23 +---
   .../broadcom/brcm80211/brcmfmac/fwsignal.c | 32
 +-
   .../wireless/broadcom/brcm80211/brcmfmac/sdio.c|  7 -
   4 files changed, 51 insertions(+), 26 deletions(-)

>>>
>>> [...]
>>>
 diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
 b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
 index 5eaac13..08272e8 100644
 --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
 +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
 @@ -198,7 +198,7 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct
 sk_buff *skb,
 int ret;
 struct brcmf_if *ifp = netdev_priv(ndev);
 struct brcmf_pub *drvr = ifp->drvr;
 -   struct ethhdr *eh = (struct ethhdr *)(skb->data);
 +   struct ethhdr *eh;
 brcmf_dbg(DATA, "Enter, bsscfgidx=%d\n", ifp->bsscfgidx);
   @@ -212,23 +212,14 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct
 sk_buff *skb,
 }
 /* Make sure there's enough room for any header */
 -   if (skb_headroom(skb) < drvr->hdrlen) {
 -   struct sk_buff *skb2;
 -
 -   brcmf_dbg(INFO, "%s: insufficient headroom\n",
 - brcmf_ifname(ifp));
 -   drvr->bus_if->tx_realloc++;
 -   skb2 = skb_realloc_headroom(skb, drvr->hdrlen);
 -   dev_kfree_skb(skb);
 -   skb = skb2;
 -   if (skb == NULL) {
 -   brcmf_err("%s: skb_realloc_headroom failed\n",
 - brcmf_ifname(ifp));
 -   ret = -ENOMEM;
 -   goto done;
 -   }
>>>
>>>
>>> What you are throwing away here is code that assures there is sufficient
>>> headroom for protocol and bus layer in the tx path, because that is
>>> determined by drvr->hdrlen. This is where the skb is handed to the driver so
>>> if you could leave the functionality above *and* assure it is writeable that
>>> would be the best solution as there is no need for all the other changes
>>> down the tx path.
>>
>> The skb_cow_head function takes the required headroom as a parameter
>> and will ensure that there is enough space, so I don't think this code
>> segment is
>> required or have I misunderstood what you mean here?
>
> I looked more into what skb_cow_head() and skb_realloc_headroom()
> actually do and it seems you are right.
>
>> Is it safe to rely on the _cow_ being done here and not further down
>> in the stack?
>> Or at least checked further down in the stack. Previous comments from
>> another patch
>> requested that the _cow_ be done close to the actual addition of the
>> header. I presume
>> it is unlikely/impossible that the functions that add header
>> information  down the stack
>> will be called without the above being done first?
>
> It is safe. During probe sequence each layer in the driver stack
> increments drvr->hdrlen with headroom it needs. So drvr->hdrlen will
> indicate the total headroom needed when .start_xmit() is called. And
> yes, the .start_xmit() is the single point of entry in the transmit
> path. So the other locations where skb_push() is done are safe.
>

OK, I will redo the patch (making it v3 + changelogs), taking this in
to account.


>>>
 +   ret = skb_cow_head(skb, drvr->hdrlen);
 +   if (ret) {
>>>
>>>
>>> So move the realloc code above here instead of simply freeing the skb.
>>>
 +   dev_kfree_skb_any(skb);
 +   goto done;
 }
   + eh = (struct ethhdr *)(skb->data);
>>>
>>>
>>> Now this is actually a separate fix so I would like a separate patch for it.
>>>
>>
>> No problem, but see final paragraph below.
>
> Let me see...

I'll split this fix out, but should I issue it in the same patch set
or as a separate patch?
And for a different patch, 

Re: [PATCH] brcm80211: brcmfmac: Ensure that incoming skb's are writable

[Arend Van Spriel]

On 21-4-2017 11:22, James Hughes wrote:
> On 20 April 2017 at 20:48, Arend van Spriel
>  wrote:
>> + linux-wireless
>>
>> On 4/20/2017 1:16 PM, James Hughes wrote:
>>>
>>> The driver was adding header information to incoming skb
>>> without ensuring the head was uncloned and hence writable.
>>>
>>> skb_cow_head has been used to ensure they are writable, however,
>>> this required some changes to error handling to ensure that
>>> if skb_cow_head failed it was not ignored.
>>>
>>> This really needs to be reviewed by someone who is more familiar
>>> with this code base to ensure any deallocation of skb's is
>>> still correct.
>>>
>>> Signed-off-by: James Hughes 
>>> ---
>>>   .../wireless/broadcom/brcm80211/brcmfmac/bcdc.c| 15 --
>>>   .../wireless/broadcom/brcm80211/brcmfmac/core.c| 23 +---
>>>   .../broadcom/brcm80211/brcmfmac/fwsignal.c | 32
>>> +-
>>>   .../wireless/broadcom/brcm80211/brcmfmac/sdio.c|  7 -
>>>   4 files changed, 51 insertions(+), 26 deletions(-)
>>>
>>
>> [...]
>>
>>> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
>>> b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
>>> index 5eaac13..08272e8 100644
>>> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
>>> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
>>> @@ -198,7 +198,7 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct
>>> sk_buff *skb,
>>> int ret;
>>> struct brcmf_if *ifp = netdev_priv(ndev);
>>> struct brcmf_pub *drvr = ifp->drvr;
>>> -   struct ethhdr *eh = (struct ethhdr *)(skb->data);
>>> +   struct ethhdr *eh;
>>> brcmf_dbg(DATA, "Enter, bsscfgidx=%d\n", ifp->bsscfgidx);
>>>   @@ -212,23 +212,14 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct
>>> sk_buff *skb,
>>> }
>>> /* Make sure there's enough room for any header */
>>> -   if (skb_headroom(skb) < drvr->hdrlen) {
>>> -   struct sk_buff *skb2;
>>> -
>>> -   brcmf_dbg(INFO, "%s: insufficient headroom\n",
>>> - brcmf_ifname(ifp));
>>> -   drvr->bus_if->tx_realloc++;
>>> -   skb2 = skb_realloc_headroom(skb, drvr->hdrlen);
>>> -   dev_kfree_skb(skb);
>>> -   skb = skb2;
>>> -   if (skb == NULL) {
>>> -   brcmf_err("%s: skb_realloc_headroom failed\n",
>>> - brcmf_ifname(ifp));
>>> -   ret = -ENOMEM;
>>> -   goto done;
>>> -   }
>>
>>
>> What you are throwing away here is code that assures there is sufficient
>> headroom for protocol and bus layer in the tx path, because that is
>> determined by drvr->hdrlen. This is where the skb is handed to the driver so
>> if you could leave the functionality above *and* assure it is writeable that
>> would be the best solution as there is no need for all the other changes
>> down the tx path.
> 
> The skb_cow_head function takes the required headroom as a parameter
> and will ensure that there is enough space, so I don't think this code
> segment is
> required or have I misunderstood what you mean here?

I looked more into what skb_cow_head() and skb_realloc_headroom()
actually do and it seems you are right.

> Is it safe to rely on the _cow_ being done here and not further down
> in the stack?
> Or at least checked further down in the stack. Previous comments from
> another patch
> requested that the _cow_ be done close to the actual addition of the
> header. I presume
> it is unlikely/impossible that the functions that add header
> information  down the stack
> will be called without the above being done first?

It is safe. During probe sequence each layer in the driver stack
increments drvr->hdrlen with headroom it needs. So drvr->hdrlen will
indicate the total headroom needed when .start_xmit() is called. And
yes, the .start_xmit() is the single point of entry in the transmit
path. So the other locations where skb_push() is done are safe.

>>
>>> +   ret = skb_cow_head(skb, drvr->hdrlen);
>>> +   if (ret) {
>>
>>
>> So move the realloc code above here instead of simply freeing the skb.
>>
>>> +   dev_kfree_skb_any(skb);
>>> +   goto done;
>>> }
>>>   + eh = (struct ethhdr *)(skb->data);
>>
>>
>> Now this is actually a separate fix so I would like a separate patch for it.
>>
> 
> No problem, but see final paragraph below.

Let me see...

>> I have a RPi3 sitting on my desk so how can I replicate the issue. It was
>> something about broadcast/multicast traffic when using AP mode and a bridge,
>> right?
>>
>> Regards,
>> Arend
> 
> See this issue for details on replication.
> https://github.com/raspberrypi/firmware/issues/673
> 
> The bridge I use is setup using a similar procedure to that described
> here.  
> 

Re: [PATCH] brcm80211: brcmfmac: Ensure that incoming skb's are writable

[James Hughes]

On 20 April 2017 at 20:48, Arend van Spriel
 wrote:
> + linux-wireless
>
> On 4/20/2017 1:16 PM, James Hughes wrote:
>>
>> The driver was adding header information to incoming skb
>> without ensuring the head was uncloned and hence writable.
>>
>> skb_cow_head has been used to ensure they are writable, however,
>> this required some changes to error handling to ensure that
>> if skb_cow_head failed it was not ignored.
>>
>> This really needs to be reviewed by someone who is more familiar
>> with this code base to ensure any deallocation of skb's is
>> still correct.
>>
>> Signed-off-by: James Hughes 
>> ---
>>   .../wireless/broadcom/brcm80211/brcmfmac/bcdc.c| 15 --
>>   .../wireless/broadcom/brcm80211/brcmfmac/core.c| 23 +---
>>   .../broadcom/brcm80211/brcmfmac/fwsignal.c | 32
>> +-
>>   .../wireless/broadcom/brcm80211/brcmfmac/sdio.c|  7 -
>>   4 files changed, 51 insertions(+), 26 deletions(-)
>>
>
> [...]
>
>> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
>> b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
>> index 5eaac13..08272e8 100644
>> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
>> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
>> @@ -198,7 +198,7 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct
>> sk_buff *skb,
>> int ret;
>> struct brcmf_if *ifp = netdev_priv(ndev);
>> struct brcmf_pub *drvr = ifp->drvr;
>> -   struct ethhdr *eh = (struct ethhdr *)(skb->data);
>> +   struct ethhdr *eh;
>> brcmf_dbg(DATA, "Enter, bsscfgidx=%d\n", ifp->bsscfgidx);
>>   @@ -212,23 +212,14 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct
>> sk_buff *skb,
>> }
>> /* Make sure there's enough room for any header */
>> -   if (skb_headroom(skb) < drvr->hdrlen) {
>> -   struct sk_buff *skb2;
>> -
>> -   brcmf_dbg(INFO, "%s: insufficient headroom\n",
>> - brcmf_ifname(ifp));
>> -   drvr->bus_if->tx_realloc++;
>> -   skb2 = skb_realloc_headroom(skb, drvr->hdrlen);
>> -   dev_kfree_skb(skb);
>> -   skb = skb2;
>> -   if (skb == NULL) {
>> -   brcmf_err("%s: skb_realloc_headroom failed\n",
>> - brcmf_ifname(ifp));
>> -   ret = -ENOMEM;
>> -   goto done;
>> -   }
>
>
> What you are throwing away here is code that assures there is sufficient
> headroom for protocol and bus layer in the tx path, because that is
> determined by drvr->hdrlen. This is where the skb is handed to the driver so
> if you could leave the functionality above *and* assure it is writeable that
> would be the best solution as there is no need for all the other changes
> down the tx path.

The skb_cow_head function takes the required headroom as a parameter
and will ensure that there is enough space, so I don't think this code
segment is
required or have I misunderstood what you mean here?

Is it safe to rely on the _cow_ being done here and not further down
in the stack?
Or at least checked further down in the stack. Previous comments from
another patch
requested that the _cow_ be done close to the actual addition of the
header. I presume
it is unlikely/impossible that the functions that add header
information  down the stack
will be called without the above being done first?

>
>> +   ret = skb_cow_head(skb, drvr->hdrlen);
>> +   if (ret) {
>
>
> So move the realloc code above here instead of simply freeing the skb.
>
>> +   dev_kfree_skb_any(skb);
>> +   goto done;
>> }
>>   + eh = (struct ethhdr *)(skb->data);
>
>
> Now this is actually a separate fix so I would like a separate patch for it.
>

No problem, but see final paragraph below.


> I have a RPi3 sitting on my desk so how can I replicate the issue. It was
> something about broadcast/multicast traffic when using AP mode and a bridge,
> right?
>
> Regards,
> Arend

See this issue for details on replication.
https://github.com/raspberrypi/firmware/issues/673

The bridge I use is setup using a similar procedure to that described
here.  
https://www.raspberrypi.org/documentation/configuration/wireless/access-point.md

I'm happy to pass over this work to you guys if you think it is
appropriate, you are the
experts on the codebase.

Re: [PATCH] brcm80211: brcmfmac: Ensure that incoming skb's are writable

[Arend van Spriel]

+ linux-wireless

On 4/20/2017 1:16 PM, James Hughes wrote:

The driver was adding header information to incoming skb
without ensuring the head was uncloned and hence writable.

skb_cow_head has been used to ensure they are writable, however,
this required some changes to error handling to ensure that
if skb_cow_head failed it was not ignored.

This really needs to be reviewed by someone who is more familiar
with this code base to ensure any deallocation of skb's is
still correct.

Signed-off-by: James Hughes 
---
  .../wireless/broadcom/brcm80211/brcmfmac/bcdc.c| 15 --
  .../wireless/broadcom/brcm80211/brcmfmac/core.c| 23 +---
  .../broadcom/brcm80211/brcmfmac/fwsignal.c | 32 +-
  .../wireless/broadcom/brcm80211/brcmfmac/sdio.c|  7 -
  4 files changed, 51 insertions(+), 26 deletions(-)



[...]


diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c 
b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
index 5eaac13..08272e8 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
@@ -198,7 +198,7 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct sk_buff 
*skb,
int ret;
struct brcmf_if *ifp = netdev_priv(ndev);
struct brcmf_pub *drvr = ifp->drvr;
-   struct ethhdr *eh = (struct ethhdr *)(skb->data);
+   struct ethhdr *eh;
  
  	brcmf_dbg(DATA, "Enter, bsscfgidx=%d\n", ifp->bsscfgidx);
  
@@ -212,23 +212,14 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct sk_buff *skb,

}
  
  	/* Make sure there's enough room for any header */

-   if (skb_headroom(skb) < drvr->hdrlen) {
-   struct sk_buff *skb2;
-
-   brcmf_dbg(INFO, "%s: insufficient headroom\n",
- brcmf_ifname(ifp));
-   drvr->bus_if->tx_realloc++;
-   skb2 = skb_realloc_headroom(skb, drvr->hdrlen);
-   dev_kfree_skb(skb);
-   skb = skb2;
-   if (skb == NULL) {
-   brcmf_err("%s: skb_realloc_headroom failed\n",
- brcmf_ifname(ifp));
-   ret = -ENOMEM;
-   goto done;
-   }


What you are throwing away here is code that assures there is sufficient 
headroom for protocol and bus layer in the tx path, because that is 
determined by drvr->hdrlen. This is where the skb is handed to the 
driver so if you could leave the functionality above *and* assure it is 
writeable that would be the best solution as there is no need for all 
the other changes down the tx path.



+   ret = skb_cow_head(skb, drvr->hdrlen);
+   if (ret) {


So move the realloc code above here instead of simply freeing the skb.


+   dev_kfree_skb_any(skb);
+   goto done;
}
  
+	eh = (struct ethhdr *)(skb->data);


Now this is actually a separate fix so I would like a separate patch for it.

I have a RPi3 sitting on my desk so how can I replicate the issue. It 
was something about broadcast/multicast traffic when using AP mode and a 
bridge, right?


Regards,
Arend

Re: [PATCH] brcm80211: brcmfmac: Ensure that incoming skb's are writable

[Arend van Spriel]

On 4/20/2017 2:09 PM, James Hughes wrote:

On 20 April 2017 at 12:31, Kalle Valo  wrote:

+ linux-wireless

James Hughes  writes:


The driver was adding header information to incoming skb
without ensuring the head was uncloned and hence writable.

skb_cow_head has been used to ensure they are writable, however,
this required some changes to error handling to ensure that
if skb_cow_head failed it was not ignored.

This really needs to be reviewed by someone who is more familiar
with this code base to ensure any deallocation of skb's is
still correct.

Signed-off-by: James Hughes 


You should also CC linux-wireless, otherwise patchwork won't see it.

--
Kalle Valo


Thanks Kalle, I wasn't subscribed to wireless, but have now done so. I
also failed to read the MAINTAINERS list correctly..

With regard to this particular patch, this is related to the recent
patches to use skb_cow_head in a number of USB net drivers to ensure
they can write headers correctly, and I suspect the same fault is
possible/likely in other drivers outside the USB net realm, as this
patch shows.

I'm not overly happy with the error handling in this patch, but that
said, the error handling over this entire driver does strike me as
suspect. Quite a few places where return codes are ignored, just in my
quick examination. So not really sure how to proceed past this patch,
if at all.


I would appreciate it if you can provide details about the code you 
consider suspect. I will respond on the patches soon.


Regards,
Arend

Re: [PATCH] brcm80211: brcmfmac: Ensure that incoming skb's are writable

[Eric Dumazet]

On Thu, 2017-04-20 at 12:16 +0100, James Hughes wrote:
> The driver was adding header information to incoming skb
> without ensuring the head was uncloned and hence writable.
> 
> skb_cow_head has been used to ensure they are writable, however,
> this required some changes to error handling to ensure that
> if skb_cow_head failed it was not ignored.
> 
> This really needs to be reviewed by someone who is more familiar
> with this code base to ensure any deallocation of skb's is
> still correct.
> 
> Signed-off-by: James Hughes 
> ---

You mention incoming skb in patch title, yet you change part of TX path.

Please split your changes in individual ones, to ease future bisections,
and ease backports as well.


Also, while it is known that TX path can deal with cloned skbs,
it is not clear why RX path has clones.

Most drivers allocate an skb, fill it, and pass it to network stack.

So please make sure all these changes are really needed.

> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c 
> b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
> index d138260..0e53c8a 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
> @@ -2719,7 +2719,7 @@ static bool brcmf_sdio_prec_enq(struct pktq *q, struct 
> sk_buff *pkt, int prec)
>  
>  static int brcmf_sdio_bus_txdata(struct device *dev, struct sk_buff *pkt)
>  {
> - int ret = -EBADE;
> + int ret = -EBADE, err;
>   uint prec;
>   struct brcmf_bus *bus_if = dev_get_drvdata(dev);
>   struct brcmf_sdio_dev *sdiodev = bus_if->bus_priv.sdio;
> @@ -2729,6 +2729,11 @@ static int brcmf_sdio_bus_txdata(struct device *dev, 
> struct sk_buff *pkt)
>   if (sdiodev->state != BRCMF_SDIOD_DATA)
>   return -EIO;
>  
> + err = skb_cow_head(pkt, bus->tx_hdrlen);
> +
> + if (err)
> + return err;
> +
>   /* Add space for the header */
>   skb_push(pkt, bus->tx_hdrlen);
>   /* precondition: IS_ALIGNED((unsigned long)(pkt->data), 2) */

Re: [PATCH] brcm80211: brcmfmac: Ensure that incoming skb's are writable

[James Hughes]

On 20 April 2017 at 12:31, Kalle Valo  wrote:
> + linux-wireless
>
> James Hughes  writes:
>
>> The driver was adding header information to incoming skb
>> without ensuring the head was uncloned and hence writable.
>>
>> skb_cow_head has been used to ensure they are writable, however,
>> this required some changes to error handling to ensure that
>> if skb_cow_head failed it was not ignored.
>>
>> This really needs to be reviewed by someone who is more familiar
>> with this code base to ensure any deallocation of skb's is
>> still correct.
>>
>> Signed-off-by: James Hughes 
>
> You should also CC linux-wireless, otherwise patchwork won't see it.
>
> --
> Kalle Valo

Thanks Kalle, I wasn't subscribed to wireless, but have now done so. I
also failed to read the MAINTAINERS list correctly..

With regard to this particular patch, this is related to the recent
patches to use skb_cow_head in a number of USB net drivers to ensure
they can write headers correctly, and I suspect the same fault is
possible/likely in other drivers outside the USB net realm, as this
patch shows.

I'm not overly happy with the error handling in this patch, but that
said, the error handling over this entire driver does strike me as
suspect. Quite a few places where return codes are ignored, just in my
quick examination. So not really sure how to proceed past this patch,
if at all.

Re: [PATCH] brcm80211: brcmfmac: Ensure that incoming skb's are writable

[Kalle Valo]

+ linux-wireless

James Hughes  writes:

> The driver was adding header information to incoming skb
> without ensuring the head was uncloned and hence writable.
>
> skb_cow_head has been used to ensure they are writable, however,
> this required some changes to error handling to ensure that
> if skb_cow_head failed it was not ignored.
>
> This really needs to be reviewed by someone who is more familiar
> with this code base to ensure any deallocation of skb's is
> still correct.
>
> Signed-off-by: James Hughes 

You should also CC linux-wireless, otherwise patchwork won't see it.

-- 
Kalle Valo

[PATCH] brcm80211: brcmfmac: Ensure that incoming skb's are writable

[James Hughes]

The driver was adding header information to incoming skb
without ensuring the head was uncloned and hence writable.

skb_cow_head has been used to ensure they are writable, however,
this required some changes to error handling to ensure that
if skb_cow_head failed it was not ignored.

This really needs to be reviewed by someone who is more familiar
with this code base to ensure any deallocation of skb's is
still correct.

Signed-off-by: James Hughes 
---
 .../wireless/broadcom/brcm80211/brcmfmac/bcdc.c| 15 --
 .../wireless/broadcom/brcm80211/brcmfmac/core.c| 23 +---
 .../broadcom/brcm80211/brcmfmac/fwsignal.c | 32 +-
 .../wireless/broadcom/brcm80211/brcmfmac/sdio.c|  7 -
 4 files changed, 51 insertions(+), 26 deletions(-)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/bcdc.c 
b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/bcdc.c
index 038a960..b9d7d08 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/bcdc.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/bcdc.c
@@ -249,14 +249,19 @@ brcmf_proto_bcdc_set_dcmd(struct brcmf_pub *drvr, int 
ifidx, uint cmd,
return ret;
 }
 
-static void
+static int
 brcmf_proto_bcdc_hdrpush(struct brcmf_pub *drvr, int ifidx, u8 offset,
 struct sk_buff *pktbuf)
 {
struct brcmf_proto_bcdc_header *h;
+   int err;
 
brcmf_dbg(BCDC, "Enter\n");
 
+   err = skb_cow_head(pktbuf, BCDC_HEADER_LEN);
+   if (err)
+   return err;
+
/* Push BDC header used to convey priority for buses that don't */
skb_push(pktbuf, BCDC_HEADER_LEN);
 
@@ -271,6 +276,8 @@ brcmf_proto_bcdc_hdrpush(struct brcmf_pub *drvr, int ifidx, 
u8 offset,
h->data_offset = offset;
BCDC_SET_IF_IDX(h, ifidx);
trace_brcmf_bcdchdr(pktbuf->data);
+
+   return 0;
 }
 
 static int
@@ -330,7 +337,11 @@ static int
 brcmf_proto_bcdc_txdata(struct brcmf_pub *drvr, int ifidx, u8 offset,
struct sk_buff *pktbuf)
 {
-   brcmf_proto_bcdc_hdrpush(drvr, ifidx, offset, pktbuf);
+   int err = brcmf_proto_bcdc_hdrpush(drvr, ifidx, offset, pktbuf);
+
+   if (err)
+   return err;
+
return brcmf_bus_txdata(drvr->bus_if, pktbuf);
 }
 
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c 
b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
index 5eaac13..08272e8 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
@@ -198,7 +198,7 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct sk_buff 
*skb,
int ret;
struct brcmf_if *ifp = netdev_priv(ndev);
struct brcmf_pub *drvr = ifp->drvr;
-   struct ethhdr *eh = (struct ethhdr *)(skb->data);
+   struct ethhdr *eh;
 
brcmf_dbg(DATA, "Enter, bsscfgidx=%d\n", ifp->bsscfgidx);
 
@@ -212,23 +212,14 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct sk_buff 
*skb,
}
 
/* Make sure there's enough room for any header */
-   if (skb_headroom(skb) < drvr->hdrlen) {
-   struct sk_buff *skb2;
-
-   brcmf_dbg(INFO, "%s: insufficient headroom\n",
- brcmf_ifname(ifp));
-   drvr->bus_if->tx_realloc++;
-   skb2 = skb_realloc_headroom(skb, drvr->hdrlen);
-   dev_kfree_skb(skb);
-   skb = skb2;
-   if (skb == NULL) {
-   brcmf_err("%s: skb_realloc_headroom failed\n",
- brcmf_ifname(ifp));
-   ret = -ENOMEM;
-   goto done;
-   }
+   ret = skb_cow_head(skb, drvr->hdrlen);
+   if (ret) {
+   dev_kfree_skb_any(skb);
+   goto done;
}
 
+   eh = (struct ethhdr *)(skb->data);
+
/* validate length for ether packet */
if (skb->len < sizeof(*eh)) {
ret = -EINVAL;
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwsignal.c 
b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwsignal.c
index a190f53..2510408 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwsignal.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwsignal.c
@@ -877,12 +877,15 @@ static void brcmf_fws_cleanup(struct brcmf_fws_info *fws, 
int ifidx)
brcmf_fws_hanger_cleanup(fws, matchfn, ifidx);
 }
 
-static u8 brcmf_fws_hdrpush(struct brcmf_fws_info *fws, struct sk_buff *skb)
+static int brcmf_fws_hdrpush(struct brcmf_fws_info *fws, struct sk_buff *skb,
+u8 *offset)
 {
struct brcmf_fws_mac_descriptor *entry = brcmf_skbcb(skb)->mac;
u8 *wlh;
u16 data_offset = 0;
u8 fillers;
+   int err;
+
__le32 pkttag = cpu_to_le32(brcmf_skbcb(skb)->htod);
__le16 pktseq = cpu_to_le16(brcmf_skbcb(skb)->htod_seq);
 
@@