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SubjectRe: [PATCH] Fix NULL dereference in rtlwifi driver
On Thu, 20 Jan 2011, Larry Finger wrote:

> On 01/20/2011 04:18 PM, Jesper Juhl wrote:
> > In drivers/net/wireless/rtlwifi/pci.c::_rtl_pci_rx_interrupt() we call
> > dev_alloc_skb(), which may fail and return NULL, but we do not check the
> > returned value against NULL before dereferencing the returned pointer.
> > This may lead to a NULL pointer dereference which means we'll crash - not
> > good.
> >
> > This patch tries to solve the issue by testing for NULL and bailing out if
> > we couldn't allocate a skb. However, I don't know this code well, so I'm
> > not sure that jumping to the 'done' label here is the correct action to
> > take. Someone more knowledgable about this code than me should definately
> > review it before it is applied anywhere.
> > While I was in the area I also moved an assignment in
> > _rtl_pci_init_rx_ring() a bit - if the dev_alloc_skb() call in that
> > function fails there's no reason to waste clock cycles assigning to the
> > local variable 'entry', we may as well do that after the NULL check and
> > potential bail out.
> >
> > Here's the proposed patch, but please don't take it as much more than a
> > bug report. If it happens to be correct, then by all means apply it, but
> > I'm not personally making any guarantees.
> >
> > Signed-off-by: Jesper Juhl <jj@chaosbits.net>
> > ---
> > pci.c | 9 ++++++++-
> > 1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > compile tested only, I don't have the hardware to test for real.
> >
> > diff --git a/drivers/net/wireless/rtlwifi/pci.c b/drivers/net/wireless/rtlwifi/pci.c
> > index 0fa36aa..5e99f89 100644
> > --- a/drivers/net/wireless/rtlwifi/pci.c
> > +++ b/drivers/net/wireless/rtlwifi/pci.c
> > @@ -619,6 +619,13 @@ static void _rtl_pci_rx_interrupt(struct ieee80211_hw *hw)
> > struct sk_buff *uskb = NULL;
> > u8 *pdata;
> > uskb = dev_alloc_skb(skb->len + 128);
> > + if (!uskb) {
> > + RT_TRACE(rtlpriv,
> > + (COMP_INTR | COMP_RECV),
> > + DBG_DMESG,
> > + ("can't alloc rx skb\n"));
> > + goto done;
> > + }
> > memcpy(IEEE80211_SKB_RXCB(uskb),
> > &rx_status,
> > sizeof(rx_status));
> > @@ -1066,9 +1073,9 @@ static int _rtl_pci_init_rx_ring(struct ieee80211_hw *hw)
> > struct sk_buff *skb =
> > dev_alloc_skb(rtlpci->rxbuffersize);
> > u32 bufferaddress;
> > - entry = &rtlpci->rx_ring[rx_queue_idx].desc[i];
> > if (!skb)
> > return 0;
> > + entry = &rtlpci->rx_ring[rx_queue_idx].desc[i];
> >
> > /*skb->dev = dev; */
> >
>
> This patch looks mostly good to me. The only change I would make is to replace
> "DBG_DMESG" in the RT_TRACE statement with "DBG_EMERG". The standard setting of
> the debug variable does not generate output for DBG_DMESG.
>
> With that change, ACK and
> Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
>

Here you go.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
---
pci.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/rtlwifi/pci.c b/drivers/net/wireless/rtlwifi/pci.c
index 0fa36aa..1758d44 100644
--- a/drivers/net/wireless/rtlwifi/pci.c
+++ b/drivers/net/wireless/rtlwifi/pci.c
@@ -619,6 +619,13 @@ static void _rtl_pci_rx_interrupt(struct ieee80211_hw *hw)
struct sk_buff *uskb = NULL;
u8 *pdata;
uskb = dev_alloc_skb(skb->len + 128);
+ if (!uskb) {
+ RT_TRACE(rtlpriv,
+ (COMP_INTR | COMP_RECV),
+ DBG_EMERG,
+ ("can't alloc rx skb\n"));
+ goto done;
+ }
memcpy(IEEE80211_SKB_RXCB(uskb),
&rx_status,
sizeof(rx_status));
@@ -641,7 +648,7 @@ static void _rtl_pci_rx_interrupt(struct ieee80211_hw *hw)
new_skb = dev_alloc_skb(rtlpci->rxbuffersize);
if (unlikely(!new_skb)) {
RT_TRACE(rtlpriv, (COMP_INTR | COMP_RECV),
- DBG_DMESG,
+ DBG_EMERG,
("can't alloc skb for rx\n"));
goto done;
}
@@ -1066,9 +1073,9 @@ static int _rtl_pci_init_rx_ring(struct ieee80211_hw *hw)
struct sk_buff *skb =
dev_alloc_skb(rtlpci->rxbuffersize);
u32 bufferaddress;
- entry = &rtlpci->rx_ring[rx_queue_idx].desc[i];
if (!skb)
return 0;
+ entry = &rtlpci->rx_ring[rx_queue_idx].desc[i];

/*skb->dev = dev; */


--
Jesper Juhl <jj@chaosbits.net> http://www.chaosbits.net/
Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please.



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