Kernel crashing in tcp_sendmsg()

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

Hi,

Fixes generally don't get merged unless they're tested as working.
Can you please report back on whether this patch resolves your issue?

Thanks.

On Fri, Jul 09, 2010 at 10:53:29AM +0100, Russell King - ARM Linux wrote:
> On Fri, Jul 09, 2010 at 11:25:13AM +0200, Bosko Radivojevic wrote:
> > I have Atmel's AT91SAM9260 based system, Linux 2.6.33.4 kernel with
> > applied at91 patch. When the system is on a heavy load it happens
> > quite often to see kernel crashed during web server execution. It
> > seems the problem it is tcp related. I tried two different web servers
> > (thttpd and lighttpd) with the same results. I tried to debug the
> > problem, but without success. Any ideas or hitns how to proceed in
> > this situtation are more than welcome.
> 
> csum_partial_copy_from_user's exception path is broken.  It has this
> function prototype:
> 
> unsigned int csum_partial_copy_from_user(const char *src, char *dst,
>   int len, int sum, int *err_ptr);
> 
> So, r0=src, r1=dst, r2=len, r3=sum, [sp]=err_ptr.
> 
> On function entry, it stacks registers like so:
> 
>                 stmfd   sp!, {r1, r2, r4 - r8, lr}
> 
> On exception:
> 
> 9001:           mov     r4, #-EFAULT
>                 ldr     r5, [fp, #4]            @ *err_ptr
>                 str     r4, [r5]
> 
> This only works if the code is using frame pointers.  This should fix it.
> Please test and provide a Tested-by: line.
> 
> Subject: Fix csum_partial_copy_from_user()
> 
> Using the parent functions frame pointer to access our arguments is
> completely wrong, whether or not we're building with frame pointers
> or not.  What we should be using is the stack pointer to get at the
> word above the registers we stacked ourselves.
> 
> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
> ---
>  arch/arm/lib/csumpartialcopyuser.S |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/lib/csumpartialcopyuser.S b/arch/arm/lib/csumpartialcopyuser.S
> index 59ff6fd..7d08b43 100644
> --- a/arch/arm/lib/csumpartialcopyuser.S
> +++ b/arch/arm/lib/csumpartialcopyuser.S
> @@ -71,7 +71,7 @@
>  		.pushsection .fixup,"ax"
>  		.align	4
>  9001:		mov	r4, #-EFAULT
> -		ldr	r5, [fp, #4]		@ *err_ptr
> +		ldr	r5, [sp, #8*4]		@ *err_ptr
>  		str	r4, [r5]
>  		ldmia	sp, {r1, r2}		@ retrieve dst, len
>  		add	r2, r2, r1
> 
> 
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