linux-ext4 - Re: Potential bug in mballoc --- reusing data blocks before txn commit

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:	Tue, 30 Sep 2008 00:21:06 +0400
From:	Alex Tomas <bzzz@....com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	Andreas Dilger <adilger@....com>, linux-ext4@...r.kernel.org
Subject: Re: Potential bug in mballoc --- reusing data blocks before txn commit

Theodore Ts'o wrote:
> I'll also note that a linked list of extents that should be freed would
> also be useful for implementing the trim command for SSD's --- and that
> this would be much more cleanly implemented via a callback from the jbd2
> layer when a commit is finished, rather than the current
> ext4_mb_poll_new_transaction() mechanism.

yes, polling is a hack as we lost commit callback long ago.

> In any case, is there a reason why the mballoc.c is using its current
> scheme, and not using kj->b_commited_data as in the original balloc.c
> code?  And was there a reason why you decided that it wasn't necessary
> to protect freed data blocks from being reused until the transaction was
> committed?

I think we don't really care about data consistency much. so I tried to save
some memory (given amount of metadata is smaller usually).


thanks, Alex

--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html