linux-kernel - Re: [PATCH 1/1] Document get_user_pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20090410110626.7931.A69D9226@jp.fujitsu.com>
Date:	Fri, 10 Apr 2009 11:17:22 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Andy Grover <andy.grover@...cle.com>
Cc:	kosaki.motohiro@...fujitsu.com, linux-kernel@...r.kernel.org,
	mingo@...hat.com, npiggin@...e.de, akpm@...ux-foundation.org
Subject: Re: [PATCH 1/1] Document get_user_pages_fast()

> +/**
> + * get_user_pages_fast() - pin user pages in memory
> + * @start:	starting user address
> + * @nr_pages:	number of pages from start to pin
> + * @write:	whether pages will be written to
> + * @pages:	array that receives pointers to the pages pinned.
> + *		Should be at least nr_pages long.
> + *
> + * Attempt to pin user pages in memory without taking mm->mmap_sem.
> + * If not successful, it will fall back to taking the lock and
> + * calling get_user_pages().
> + *
> + * Returns number of pages pinned. This may be fewer than the number
> + * requested. If nr_pages is 0 or negative, returns 0. If no pages
> + * were pinned, returns -errno.
> + */
>  int __attribute__((weak)) get_user_pages_fast(unsigned long start,
>  				int nr_pages, int write, struct page **pages)
>  {

There is one problem.
gup and get_page() don't provide any page pinning.

get_page() only gurantee not freed. but don't gurantee to prevent page
reclaim and Cow change owner process.

Yes, current all gup caller have serious bug. especially direct-io, aio, bio
are broken.





--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/