linux-kernel - Re: NULL pointer due to malformed bcache bio

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, 10 Apr 2013 15:49:14 -0700
From:	Kent Overstreet <koverstreet@...gle.com>
To:	Mike Snitzer <snitzer@...hat.com>
Cc:	linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org,
	dm-devel@...hat.com, axboe@...nel.dk
Subject: Re: NULL pointer due to malformed bcache bio

On Wed, Apr 10, 2013 at 04:54:40PM -0400, Mike Snitzer wrote:
> Hey,
> 
> So DM core clearly needs to be more defensive about the possibility for
> a NULL return from bio_alloc_bioset() given I'm hitting a NULL pointer
> in DM's alloc_tio() because nr_iovecs=512.  bio_alloc_bioset()'s call to
> bvec_alloc() only supports nr_iovecs up to BIO_MAX_PAGES (256).
> 
> Seems bcache should be using bio_get_nr_vecs() or something else?
> 
> But by using a bcache bucket size of 2MB, with the bcache staged in
> Jens' for-next, I've caused bcache to issue bios with nr_iovecs=512:

Argh. Why is dm using bi_max_vecs instead of bi_vcnt? I could hack
around this in bcache but I think dm is doing the wrong thing here.

Unless I've missed something in my testing (and bcache's BIO_MAX_PAGES
check isn't quite right, actually) bcache _is_ splitting its bios
whenever bio_segments(bio) > BIO_MAX_PAGES, it's only bi_max_vecs that's
potentially > BIO_MAX_PAGES.
--
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/