From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Tue, 25 Apr 2017 15:51:38 +0100 Subject: [PATCH] arm64: fix the overlap between the kernel image and vmalloc address In-Reply-To: References: <1493025729-21505-1-git-send-email-zhongjiang@huawei.com> <20170424104456.GA4343@leverpostej> <58FDFD90.8050300@huawei.com> <20170424155125.GA5972@leverpostej> Message-ID: <20170425145138.GE3792@leverpostej> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Apr 24, 2017 at 10:52:08AM -0700, Laura Abbott wrote: > On 04/24/2017 08:51 AM, Mark Rutland wrote: > > On Mon, Apr 24, 2017 at 09:28:48PM +0800, zhong jiang wrote: > >> /* > >> * Walk a vmap address to the struct page it maps. > >> */ > >> @@ -244,6 +280,9 @@ struct page *vmalloc_to_page(const void *vmalloc_addr) > >> */ > >> VIRTUAL_BUG_ON(!is_vmalloc_or_module_addr(vmalloc_addr)); > >> > >> + if (is_kernel_image_addr(vmalloc_addr)) > >> + return kernel_image_to_page(vmalloc_addr, pgd); > > > > It's not clear to me that this is the right place for this to live. > > > > It might be best to code the kernel image logic directly in kcore (and > > kmem), assuming everyone's OK with that approach. > > > > That will fix kcore and kmem but this will show up in other places too. True. > We've gone through and made sure that virt_addr_valid returns > true if and only if virt_to_page returns a valid address. I don't know > if we can make as strong a claim about is_vmalloc_addr and > vmalloc_to_page in all cases but is_vmalloc_addr should not return true > for the kernel image. That would at least let kcore fall back to > kern_addr_valid which should correctly handle the kernel image. That would largely be my preference. My fear is that other users of is_vmalloc_addr() are doing the right thing for the kernel image today (e.g. not doing virt_to_phys()), because they see it as a vmalloc addr. So we might have to audit all of those. > The suggestion to move the kernel image out of VMALLOC_START/VMALLOC_END > seems like the best approach although I haven't tried a prototype > at all. Given that (AFAICT) we're the only architecture that puts the kernel in the vmalloc area, I agree that this is likely to be the simplest correct approach. The interaction with KASLR is somewhat unfortunate. Thanks, Mark.