linux-kernel - Re: - eepro100-avoid-potential-null-pointer-deref-in-speedo_init_rx

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Date:	Mon, 01 Oct 2007 13:54:14 -0700
From:	"Kok, Auke" <auke-jan.h.kok@...el.com>
To:	jesper.juhl@...il.com
CC:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: - eepro100-avoid-potential-null-pointer-deref-in-speedo_init_rx_ring.patch
 removed from -mm tree

akpm@...ux-foundation.org wrote:
> The patch titled
>      eepro100: Avoid potential NULL pointer deref in speedo_init_rx_ring()
> has been removed from the -mm tree.  Its filename was
>      eepro100-avoid-potential-null-pointer-deref-in-speedo_init_rx_ring.patch
> 
> This patch was dropped because an updated version will be merged
> 
> ------------------------------------------------------
> Subject: eepro100: Avoid potential NULL pointer deref in speedo_init_rx_ring()
> From: Jesper Juhl <jesper.juhl@...il.com>
> 
> In a low memory situation, if you are very unlucky, the speedo_init_rx_ring()
> function may cause a NULL pointer deref.
> 
> The problem is in the case where we can't allocate even a single skb for
> the RX ring.  In this case 'last_rxf' will be NULL when we break out of
> the loop and the line
>     last_rxf->status = cpu_to_le32(0xC0000002);	/* '2' is flag value only. */
> will cause a NULL pointer dereference.
> 
> To fix this properly we need to be return an error from speedo_init_rx_ring()
> and have the caller (speedo_open()) catch and propagate the error, as well as
> undo anything done to setup the device so far.
> 
> This patch adds a check to catch the unlucky case of not even a single skb
> being available and adds code in the caller to catch the error and release the
> device properly.
> 
> For a user who hits this problem, this makes the difference between her device
> not being opened and a kernel crash.  Clearly a non functional NIC if
> preferable to a kernel crash - especially since setting up the device can
> easily be retried later after freeing up some memory; a kernel crash is not as
> easy to recover from.
> 
> The problem was initially spotted by the Coverity checker.
> 
> Signed-off-by: Jesper Juhl <jesper.juhl@...il.com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>


is this actually a problem? everybody should be running e100. I'm surprised to see
a patch for eepro100, just before it gets removed...

Auke
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