linux-kernel - Re: [PATCH] usb/mcs7830: Don't use buffers from stack for USB transfers

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:	Wed, 21 Jan 2009 00:17:18 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	David Miller <davem@...emloft.net>
Cc:	ceggers@....de, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH] usb/mcs7830: Don't use buffers from stack for USB transfers

On Tuesday 20 January 2009, David Miller wrote:
> You cannot DMA from/to the kernel stack, because it might not be in
> the aliased linear mapping of physical memory.  It could even be
> vmalloc()'d memory on some platforms.

Ok, I see. It seems a bit of a waste to do a kmalloc for something
that is guaranteed to be just a few bytes, but allocating the
buffer per-device would mean another mutex, which has about the
same overhead, so I'm basically ok with the patch.

> +       buffer = kmalloc(size, GFP_NOIO);

GFP_NOIO seems out of place in a network driver: there is nothing
wrong with waiting for I/O here, so plain GFP_KERNEL should be fine.

> +       if (buffer == NULL)
> +               return -ENOMEM;

I'd prefer to write 

	if (!buffer)

here, as I do elsewhere in the driver.

Otherwise,

Acked-by: Arnd Bergmann <arnd@...db.de>
--
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/