linux-kernel - Re: [dm-devel] [PATCH 0/4] dm verity: add support for error correction

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:	Sat, 7 Nov 2015 10:29:05 -0500 (EST)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	Sami Tolvanen <samitolvanen@...gle.com>
cc:	device-mapper development <dm-devel@...hat.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>,
	Mike Snitzer <snitzer@...hat.com>,
	Mandeep Baines <msb@...omium.org>,
	linux-kernel@...r.kernel.org, Mark Salyzyn <salyzyn@...gle.com>
Subject: Re: [dm-devel] [PATCH 0/4] dm verity: add support for error
 correction



On Fri, 6 Nov 2015, Sami Tolvanen wrote:

> On Fri, Nov 06, 2015 at 10:05:24PM +0100, Zdenek Kabelac wrote:
> > So how do you want to correctly 'restore'  missing full sectors
> > with just 0.8% data overhead ??
> 
> We use interleaving. Each byte in a 4k block is part of a different
> Reed-Solomon block, which means an entire lost 4k data block looks like a
> single error. When we also spread the bytes that form a single Reed-Solomon
> block across the partition, we end up being able to correct several
> megabytes of consecutive corrupted blocks with very small space overhead.
> 
> Sami

But the patch doesn't do any correction in case of I/O error - it just 
returns the bio with I/O error.

BTW. the function verity_fec_alloc_buffers does vzalloc and GFP_KERNEL 
kmalloc inside I/O handling code - that shouldn't be done - you should 
preallocate the data structures when the device is loaded.

Mikulas
--
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/