linux-kernel - [PATCH] ATM, Solos PCI ADSL2+: Don't deref NULL pointer if net_ratelimit() and alloc

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Message-ID: <alpine.LNX.2.00.1102132142460.18930@swampdragon.chaosbits.net>
Date:	Sun, 13 Feb 2011 21:49:32 +0100 (CET)
From:	Jesper Juhl <jj@...osbits.net>
To:	linux-kernel@...r.kernel.org
cc:	Chas Williams <chas@....nrl.navy.mil>,
	linux-atm-general@...ts.sourceforge.net, netdev@...r.kernel.org,
	Nathan Williams <nathan@...verse.com.au>,
	David Woodhouse <dwmw2@...radead.org>,
	Treker Chen <treker@...o.com>
Subject: [PATCH] ATM, Solos PCI ADSL2+: Don't deref NULL pointer if
 net_ratelimit() and alloc_skb() interact badly.

If alloc_skb() fails to allocate memory and returns NULL then we want to 
return -ENOMEM from drivers/atm/solos-pci.c::popen() regardless of the 
value of net_ratelimit(). The way the code is today, we may not return if 
net_ratelimit() returns 0, then we'll proceed to pass a NULL pointer to 
skb_put() which will blow up in our face.
This patch ensures that we always return -ENOMEM on alloc_skb() failure 
and only let the dev_warn() be controlled by the value of net_ratelimit().

Signed-off-by: Jesper Juhl <jj@...osbits.net>
---
 solos-pci.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/atm/solos-pci.c b/drivers/atm/solos-pci.c
index 73fb1c4..25ef1a4 100644
--- a/drivers/atm/solos-pci.c
+++ b/drivers/atm/solos-pci.c
@@ -866,8 +866,9 @@ static int popen(struct atm_vcc *vcc)
 	}
 
 	skb = alloc_skb(sizeof(*header), GFP_ATOMIC);
-	if (!skb && net_ratelimit()) {
-		dev_warn(&card->dev->dev, "Failed to allocate sk_buff in popen()\n");
+	if (!skb) {
+		if (net_ratelimit())
+			dev_warn(&card->dev->dev, "Failed to allocate sk_buff in popen()\n");
 		return -ENOMEM;
 	}
 	header = (void *)skb_put(skb, sizeof(*header));


-- 
Jesper Juhl <jj@...osbits.net>            http://www.chaosbits.net/
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