linux-kernel - Re: [PATCH] xhci: use dma_alloc_coherent with fully cleared 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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <54E5FBB1.2060300@linux.intel.com>
Date:	Thu, 19 Feb 2015 17:05:21 +0200
From:	Mathias Nyman <mathias.nyman@...ux.intel.com>
To:	Tim Chen <tim.c.chen@...ux.intel.com>
CC:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, "H. Peter Anvin" <hpa@...or.com>,
	Akinobu Mita <akinobu.mita@...il.com>,
	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>,
	Alan Stern <stern@...land.harvard.edu>, ak <ak@...ux.intel.com>
Subject: Re: [PATCH] xhci: use dma_alloc_coherent with fully cleared pages

On 19.02.2015 02:34, Tim Chen wrote:
> 
> 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.
> 
> This patch reverts xhci the use the old behavior to avoid the hang.  XHCI should
> do a proper fix to avoid this un-allocated memory.
> 
> Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
> Cc: <stable@...r.kernel.org> # 3.16+
> ---
>  drivers/usb/host/xhci-mem.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> index 5cb3d7a..39e7196 100644
> --- a/drivers/usb/host/xhci-mem.c
> +++ b/drivers/usb/host/xhci-mem.c
> @@ -1658,7 +1658,7 @@ static int scratchpad_alloc(struct xhci_hcd *xhci, gfp_t flags)
>  		goto fail_sp;
>  
>  	xhci->scratchpad->sp_array = dma_alloc_coherent(dev,
> -				     num_sp * sizeof(u64),
> +				     PAGE_ALIGN(num_sp * sizeof(u64)),
>  				     &xhci->scratchpad->sp_dma, flags);
>  	if (!xhci->scratchpad->sp_array)
>  		goto fail_sp2;
> 

Thanks for figuring out that the issue was in allocation of scratchpad memory.

Turns out we don't calculate the num_sp correctly in the first place, we didn't include
the additional high order field of the max scratchpad buffers xhci tells we should reserve.
I got a patch for this and will send it to forward to Greg once 3.20-rc1 is tagged

-Mathias
--
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/