linux-kernel - Re: [PATCH 9/9] hugetlb: add corrupted hugepage counter

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <20100819015752.GB5762@localhost>
Date:	Thu, 19 Aug 2010 09:57:52 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	Jun'ichi Nomura <j-nomura@...jp.nec.com>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 9/9] hugetlb: add corrupted hugepage counter

> +void increment_corrupted_huge_page(struct page *page);
> +void decrement_corrupted_huge_page(struct page *page);

nitpick: increment/decrement are not verbs.

> +void increment_corrupted_huge_page(struct page *hpage)
> +{
> +	struct hstate *h = page_hstate(hpage);
> +	spin_lock(&hugetlb_lock);
> +	h->corrupted_huge_pages++;
> +	spin_unlock(&hugetlb_lock);
> +}
> +
> +void decrement_corrupted_huge_page(struct page *hpage)
> +{
> +	struct hstate *h = page_hstate(hpage);
> +	spin_lock(&hugetlb_lock);
> +	BUG_ON(!h->corrupted_huge_pages);

There is no point to have BUG_ON() here:

/*
 * Don't use BUG() or BUG_ON() unless there's really no way out; one
 * example might be detecting data structure corruption in the middle
 * of an operation that can't be backed out of.  If the (sub)system
 * can somehow continue operating, perhaps with reduced functionality,
 * it's probably not BUG-worthy.
 *
 * If you're tempted to BUG(), think again:  is completely giving up
 * really the *only* solution?  There are usually better options, where
 * users don't need to reboot ASAP and can mostly shut down cleanly.
 */

And there is a race case that (corrupted_huge_pages==0)!
Suppose the user space calls unpoison_memory() on a good pfn, and the page
happen to be hwpoisoned between lock_page() and TestClearPageHWPoison(),
corrupted_huge_pages will go negative.

Thanks,
Fengguang

> +	h->corrupted_huge_pages--;
> +	spin_unlock(&hugetlb_lock);
> +}
--
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/