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SubjectRe: [GIT pull] futex fixes for 2.6.31
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On Wed, 2009-06-24 at 21:48 +0200, Thomas Gleixner wrote:
> Linus,
>
> Please pull the latest futexes-for-linus git tree from:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git futexes-for-linus
>
> Thanks,
>
> tglx
>
> ------------------>
> Thomas Gleixner (1):
> futex: Fix the write access fault problem for real
>
>
> kernel/futex.c | 45 ++++++++++++++++++++++++---------------------
> 1 files changed, 24 insertions(+), 21 deletions(-)
>
> diff --git a/kernel/futex.c b/kernel/futex.c
> index 80b5ce7..1c33711 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -284,6 +284,25 @@ void put_futex_key(int fshared, union futex_key *key)
> drop_futex_key_refs(key);
> }
>
> +/*
> + * fault_in_user_writeable - fault in user address and verify RW access
> + * @uaddr: pointer to faulting user space address
> + *
> + * Slow path to fixup the fault we just took in the atomic write
> + * access to @uaddr.
> + *
> + * We have no generic implementation of a non destructive write to the
> + * user address. We know that we faulted in the atomic pagefault
> + * disabled section so we can as well avoid the #PF overhead by
> + * calling get_user_pages() right away.
> + */
> +static int fault_in_user_writeable(u32 __user *uaddr)
> +{
> + int ret = get_user_pages(current, current->mm, (unsigned long)uaddr,
> + sizeof(*uaddr), 1, 0, NULL, NULL);
The 4th parameter of get_user_pages means page number. sizeof(*uaddr) is equal to
4, so you want 4 pages?

Yanmin


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