Re: [PATCH] ia64: validate user arguments incsum_partial_copy_from_user

From: Mikulas Patocka
Date: Fri Feb 07 2014 - 11:05:25 EST


It actually turns out that the check in csum_partial_copy_from_user is
pointless (the check is already done in csum_and_copy_from_user that is
the only caller of csum_partial_copy_from_user).

So, please ignore this patch - we need to clean up alpha and x86
implementation of csum_partial_copy_from_user and not add this pointless
check to ia64.

Mikulas


On Thu, 23 Jan 2014, Mikulas Patocka wrote:

> ia64: validate user arguments in csum_partial_copy_from_user
>
> csum_partial_copy_from_user needs to validate that the argument points to
> userspace and not kernelspace (see for example commit
> 3ddc5b46a8e90f3c9251338b60191d0a804b0d92). Consequently, we need to use
> copy_from_user instead of __copy_from_user.
>
> We also need to change csum_partial_copy_nocheck - this function is called
> with src pointing to kernel space, so we call set_fs(KERNEL_DS) to prevent
> copy_from_user from failing.
>
> Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
>
> ---
> arch/ia64/lib/csum_partial_copy.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
> Index: linux-2.6-ia64/arch/ia64/lib/csum_partial_copy.c
> ===================================================================
> --- linux-2.6-ia64.orig/arch/ia64/lib/csum_partial_copy.c 2014-01-24 02:40:10.000000000 +0100
> +++ linux-2.6-ia64/arch/ia64/lib/csum_partial_copy.c 2014-01-24 03:05:26.000000000 +0100
> @@ -116,8 +116,12 @@ csum_partial_copy_from_user(const void _
> * scared.
> */
>
> - if (__copy_from_user(dst, src, len) != 0 && errp)
> - *errp = -EFAULT;
> + if (copy_from_user(dst, src, len) != 0) {
> + if (*errp)
> + *errp = -EFAULT;
> + memset(dst, 0, len);
> + return psum;
> + }
>
> result = do_csum(dst, len);
>
> @@ -133,8 +137,13 @@ EXPORT_SYMBOL(csum_partial_copy_from_use
> __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;
> }
>
> EXPORT_SYMBOL(csum_partial_copy_nocheck);
>
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