[PATCH, 2.4] wan sdla: fix probable security hole

[Horms <horms@verge.net.au>]

>  From: Chris Wright <chrisw@osdl.org>
>  Date: Mon, 19 Apr 2004 08:26:30 +0000 (-0400)
>  Subject: [PATCH] wan sdla:  fix probable security hole
>  X-Git-Tag: v2.6.6-rc2
>  X-Git-Url: http://www.kernel.org/git/?p=linux/kernel/git/tglx/history.git;a=commitdiff;h=98cd917c1ac348d5cd94beabecc3011dcaa0a0f2
>
>  [PATCH] wan sdla:  fix probable security hole
>
>  > [BUG] minor
>  > /home/kash/linux/linux-2.6.5/drivers/net/wan/sdla.c:1206:sdla_xfer:
>  > ERROR:TAINT: 1201:1206:Passing unbounded user value "(mem).len" as arg 0
>  > to function "kmalloc", which uses it unsafely in model
>  > [SOURCE_MODEL=(lib,copy_from_user,user,taintscalar)]
>  > [SINK_MODEL=(lib,kmalloc,user,trustingsink)]  [MINOR]  [PATH=] [Also
>  > used at, line 1219 in argument 0 to function "kmalloc"]
>  > static int sdla_xfer(struct net_device *dev, struct sdla_mem *info, int
>  > read)
>  > {
>  > 	struct sdla_mem mem;
>  > 	char	*temp;
>  >
>  > Start --->
>  > 	if(copy_from_user(&mem, info, sizeof(mem)))
>  > 		return -EFAULT;
>  >
>  > 	if (read)
>  > 	{
>  > Error --->
>  > 		temp = kmalloc(mem.len, GFP_KERNEL);
>  > 		if (!temp)
>  > 			return(-ENOMEM);
>  > 		sdla_read(dev, mem.addr, temp, mem.len);
>
>  Hrm, I believe you could use this to read 128k of kernel memory.
>  sdla_read() takes len as a short, whereas mem.len is an int.  So,
>  if mem.len == 0x20000, the allocation could still succeed.  When cast
>  to short, len will be 0x0, causing the read loop to copy nothing into
>  the buffer.  At least it's protected by a capable() check.  I don't
>  know what proper upper bound is for this hardware, or how much it's
>  used/cared about.  Simple memset() is trivial fix.

This seems to be applicable to 2.4

Signed-Off-By: Horms <horms@verge.net.au>

diff --git a/drivers/net/wan/sdla.c b/drivers/net/wan/sdla.c
index 75fa993..fe74a21 100644
--- a/drivers/net/wan/sdla.c
+++ b/drivers/net/wan/sdla.c
@@ -1201,6 +1201,7 @@ static int sdla_xfer(struct net_device *
 		temp = kmalloc(mem.len, GFP_KERNEL);
 		if (!temp)
 			return(-ENOMEM);
+		memset(temp, 0, mem.len);
 		sdla_read(dev, mem.addr, temp, mem.len);
 		if(copy_to_user(mem.data, temp, mem.len))
 		{