linux-ext4 - Re: [PATCH 1/2] ext4: mballoc

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, 30 May 2020 04:57:39 +0000
From:   Alex Zhuravlev <azhuravlev@...mcloud.com>
To:     "Theodore Y. Ts'o" <tytso@....edu>
CC:     "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 1/2] ext4:  mballoc - prefetching for bitmaps

> On 28 May 2020, at 17:47, Theodore Y. Ts'o <tytso@....edu> wrote:
> 
> What are you trying to do here?  If nr > 0, we return; if nr < 0, we
> BUG() --- but nr is an unsigned int, so we never can trigger --- which
> was the warning reported by the kbuild test bot.  So we will only get
> past this point if ac_prefetch == group.  But ac_prefetch appears to
> be the last group that we prefetched, so it's not clear that the logic
> is correct here.

You’re right, this part “evolved” since the initial version, but I forgot to make it clear.
Basically this should be replaced with:

If (ac->ac_prefetch != group)
	return;

ac->ac_prefetch is just a cursor for the current process.

Thanks, Alex