[3.11.y.z extended stable] Patch "alpha: fix broken network checksum" has been added to staging queue

[Mikulas Patocka]

Hi

That patch is needed on 3.12 and 3.13, you don't need to backport it to
older kernels.

If you didn't backport 3ddc5b46a8e90f3c9251338b60191d0a804b0d92, you don't 
need to backport 0ef38d70d4118b2ce1a538d14357be5ff9dc2bbd as well.

Mikulas


On Wed, 5 Feb 2014, Luis Henriques wrote:

> This is a note to let you know that I have just added a patch titled
> 
>     alpha: fix broken network checksum
> 
> to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
> which can be found at:
> 
>  http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue
> 
> If you, or anyone else, feels it should not be added to this tree, please 
> reply to this email.
> 
> For more information about the 3.11.y.z tree, see
> https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
> 
> Thanks.
> -Luis
> 
> ------
> 
> >From bc7fb262adc1386a814f4d17a88a1b5bd413562a Mon Sep 17 00:00:00 2001
> From: Mikulas Patocka <mpatocka at redhat.com>
> Date: Wed, 22 Jan 2014 23:04:33 -0500
> Subject: alpha: fix broken network checksum
> 
> commit 0ef38d70d4118b2ce1a538d14357be5ff9dc2bbd upstream.
> 
> The patch 3ddc5b46a8e90f3c9251338b60191d0a804b0d92 breaks networking on
> alpha (there is a follow-up fix 5cfe8f1ba5eebe6f4b6e5858cdb1a5be4f3272a6,
> but networking is still broken even with the second patch).
> 
> The patch 3ddc5b46a8e90f3c9251338b60191d0a804b0d92 makes
> csum_partial_copy_from_user check the pointer with access_ok. However,
> csum_partial_copy_from_user is called also from csum_partial_copy_nocheck
> and csum_partial_copy_nocheck is called on kernel pointers and it is
> supposed not to check pointer validity.
> 
> This bug results in ssh session hangs if the system is loaded and bulk
> data are printed to ssh terminal.
> 
> This patch fixes csum_partial_copy_nocheck to call set_fs(KERNEL_DS), so
> that access_ok in csum_partial_copy_from_user accepts kernel-space
> addresses.
> 
> Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
> Signed-off-by: Matt Turner <mattst88 at gmail.com>
> Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
> ---
>  arch/alpha/lib/csum_partial_copy.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/alpha/lib/csum_partial_copy.c b/arch/alpha/lib/csum_partial_copy.c
> index 40736da..1d2ef5a 100644
> --- a/arch/alpha/lib/csum_partial_copy.c
> +++ b/arch/alpha/lib/csum_partial_copy.c
> @@ -373,6 +373,11 @@ csum_partial_copy_from_user(const void __user *src, void *dst, int len,
>  __wsum
>  csum_partial_copy_nocheck(const void *src, void *dst, int len, __wsum sum)
>  {
> -	return csum_partial_copy_from_user((__force const void __user *)src,
> -			dst, len, sum, NULL);
> +	__wsum checksum;
> +	mm_segment_t oldfs = get_fs();
> +	set_fs(KERNEL_DS);
> +	checksum = csum_partial_copy_from_user((__force const void __user *)src,
> +						dst, len, sum, NULL);
> +	set_fs(oldfs);
> +	return checksum;
>  }
> --
> 1.8.3.2
>