linux-kernel - Re: [PATCH] pci-dma: Fix x86 dma_alloc_coherent to fully clear all pages returned

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]

Date:	Mon, 02 Feb 2015 19:39:18 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Jiri Slaby <jslaby@...e.cz>, Tim Chen <tim.c.chen@...ux.intel.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Akinobu Mita <akinobu.mita@...il.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-usb@...r.kernel.org, stable <stable@...r.kernel.org>
Subject: Re: [PATCH] pci-dma: Fix x86 dma_alloc_coherent to fully clear all
 pages returned

Hello.

On 02/02/2015 05:02 PM, Jiri Slaby wrote:

>> From: Tim Chen <tim.c.chen@...ux.intel.com>
>> Subject: [PATCH] pci-dma: Fix x86 dma_alloc_coherent to fully clear all pages returned


>> Commit d92ef66c4f8f ("x86: make dma_alloc_coherent() return zeroed memory
>> if CMA is enabled") changed the dma_alloc_coherent page clearance from
>> using an __GFP_ZERO in page allocation to not setting the flag but doing
>> an explicit memory clear at the end.

>> However the memory clear only covered the memory size that
>> was requested, but may not be up to the full extent of the
>> last page, if the total pages returned exceed the
>> memory size requested.  This behavior has caused problem with XHCI
>> and caused it to hang:

>> kernel: xhci_hcd 0000:00:14.0: Stopped the command ring failed, maybe the host is dead
>> kernel: xhci_hcd 0000:00:14.0: Abort command ring failed
>> kernel: xhci_hcd 0000:00:14.0: HC died; cleaning up
>> kernel: xhci_hcd 0000:00:14.0: Error while assigning device slot ID
>> kernel: xhci_hcd 0000:00:14.0: Max number of devices this xHCI host supports is 64.

>> Other drivers may have similar issue if it assumes that the pages
>> allocated are completely zeroed.

>> This patch ensures that the pages returned are fully cleared.

>> Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
>> Cc: <stable@...r.kernel.org> # 3.16+

>> ---
>>   arch/x86/kernel/pci-dma.c | 2 ++
>>   1 file changed, 2 insertions(+)

>> diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
>> index a25e202..e9d8dee 100644
>> --- a/arch/x86/kernel/pci-dma.c
>> +++ b/arch/x86/kernel/pci-dma.c
>> @@ -125,6 +125,8 @@ again:
>>
>>   		return NULL;
>>   	}
>> +	/* round up to full page size */
>> +	size = (size + ~PAGE_MASK) & PAGE_MASK;

> Hi, is this an open-coded version of PAGE_ALIGN?

    Yes, it appears so. :-)

WBR, Sergei

--
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/