Re: [PATCH] brcm80211: brcmfmac: Ensure that incoming skb's are writable
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, should I base it on the _cow_ version patch or the original version? > >>> I have a RPi3 sittin
Re: [PATCH] brcm80211: brcmfmac: Ensure that incoming skb's are writable
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. > https://www.raspberrypi.org/documentation/configuration/wireless/access-point.md > > I'm happy
Re: [PATCH] brcm80211: brcmfmac: Ensure that incoming skb's are writable
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
+ 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
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
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
+ 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