linux-kernel - Re: [PATCH 3/4] UBI: Fastmap: Care about the protection queue

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] [day] [month] [year] [list]

Date:	Mon, 20 Oct 2014 22:46:37 +0200
From:	Richard Weinberger <richard@....at>
To:	dedekind1@...il.com
CC:	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] UBI: Fastmap: Care about the protection queue

Am 20.10.2014 um 17:40 schrieb Artem Bityutskiy:
> Also, say, PEB X is in the work queue waiting for erasure. Fastmap comes
> along and saves it as "must be erased" in the fastmap. Fastmap finishes
> its job, PEB X gets erased, and I write my data there, so PEB X is
> referred to by LEB Y. Now I have power cut. Then I attach the flash
> again. Surely it is not that fastmap just erases PEB X and I lose the
> contents of LEB Y?

After reading my mail again, I think my answer was not clear.
Please let me explain in detail.

PEB X waits for erasure. In this state it can get erased and will be moved into
the free RB tree.
If a new PEB is requested from UBI it will not get served from the free RB tree,
instead it will come from the pool. I.e. There is no way that the freshly erased PEB
will immediately used. If a a fastmap was written while PEB was queued for erasure
and a power cut happens after the erasure it will be erased again. This does not harm.
But it can never ever happen that the same PEB will be in a pool (and therefore maybe used)
and scheduled for erase. A freshly erased PEB can only be used after wandering into the pool.
But this would require a refill-pool operation first an a write of the fastmap, the said PEB
cannot be listed as erase work in the fastmap then.

Thanks,
//richard
--
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/