linux-kernel - Re: [PATCH] ARM: DMA: Fix kzalloc flags in __iommu_alloc

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 for Android: free password hash cracker in your pocket

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

Message-ID: <10532762.PXKTQM8KjH@wuerfel>
Date:	Mon, 08 Dec 2014 11:24 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Alexandre Courbot <acourbot@...dia.com>,
	Russell King <linux@....linux.org.uk>,
	Marek Szyprowski <m.szyprowski@...sung.com>, gnurou@...il.com,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	linux-kernel@...r.kernel.org, Thierry Reding <treding@...dia.com>
Subject: Re: [PATCH] ARM: DMA: Fix kzalloc flags in __iommu_alloc_buffer()

On Monday 08 December 2014 17:39:27 Alexandre Courbot wrote:
> There doesn't seem to be any valid reason to allocate the pages array
> with the same flags as the buffer itself. Doing so can eventually lead
> to the following safeguard in mm/slab.c to be hit:
> 
> BUG_ON(flags & GFP_SLAB_BUG_MASK);
> 
> This happens when buffers are allocated with __GFP_DMA32 or
> __GFP_HIGHMEM.
> 
> Fix this by allocating the pages array with GFP_KERNEL to follow what is
> done elsewhere in this file. Using GFP_KERNEL in __iommu_alloc_buffer()
> is safe because atomic allocations are handled by __iommu_alloc_atomic().
> 

I think you need to carry over the GFP_ATOMIC flag if that is set by the
caller, but not the GFP_HIGHMEM or GFP_DMA32. Not sure if it's better
to mask out flags from the caller mask, or to start with GFP_KERNEL
and adding in extra bits.

	Arnd
--
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/