From: "Yuanxiaofeng (XiAn)" <yuanxiaofeng1@huawei.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "keescook@chromium.org" <keescook@chromium.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH RFC] usercopy: optimize stack check flow when the page-spanning test is disabled
Date: Tue, 14 Aug 2018 13:02:55 +0000 [thread overview]
Message-ID: <494CFD22286B8448AF161132C5FE9A985B624E05@dggema521-mbx.china.huawei.com> (raw)
In-Reply-To: <20180814123454.GA25328@bombadil.infradead.org>
1, When the THREAD_SIZE is less than PAGE_SIZE, the stack will allocate memory by kmem_cache_alloc_node(), it's slab memory and will execute __check_heap_object().
2, When CONFIG_HARDENED_USERCOPY_PAGESPAN is enabled, the multiple-pages stacks will do some check in check_page_span().
So, I set some restrictions to make sure the useful check will not be skipped.
-----Original Message-----
From: Matthew Wilcox [mailto:willy@infradead.org]
Sent: Tuesday, August 14, 2018 8:35 PM
To: Yuanxiaofeng (XiAn)
Cc: keescook@chromium.org; linux-mm@kvack.org; linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC] usercopy: optimize stack check flow when the
On Tue, Aug 14, 2018 at 08:17:31PM +0800, Xiaofeng Yuan wrote:
> The check_heap_object() checks the spanning multiple pages and slab.
> When the page-spanning test is disabled, the check_heap_object() is
> redundant for spanning multiple pages. However, the kernel stacks are
> multiple pages under certain conditions: CONFIG_ARCH_THREAD_STACK_ALLOCATOR
> is not defined and (THREAD_SIZE >= PAGE_SIZE). At this point, We can skip
> the check_heap_object() for kernel stacks to improve performance.
> Similarly, the virtually-mapped stack can skip check_heap_object() also,
> beacause virt_addr_valid() will return.
Why not just check_stack_object() first, then check_heap_object() second?
next prev parent reply other threads:[~2018-08-14 13:03 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-14 12:17 [PATCH RFC] usercopy: optimize stack check flow when the Xiaofeng Yuan
2018-08-14 12:34 ` Matthew Wilcox
2018-08-14 13:02 ` Yuanxiaofeng (XiAn) [this message]
2018-08-14 13:09 ` [PATCH RFC] usercopy: optimize stack check flow when the page-spanning test is disabled Matthew Wilcox
2018-08-14 18:54 ` Kees Cook
2018-08-15 11:59 ` Yuanxiaofeng (XiAn)
2018-08-14 12:20 Xiaofeng Yuan
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