linux-kernel - RE: [PATCH 1/2] efivars: Check max

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 4 Apr 2013 16:00:36 +0000
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Richard Weinberger <richard@....at>,
	"Fleming, Matt" <matt.fleming@...el.com>
CC:	"cbouatmailru@...il.com" <cbouatmailru@...il.com>,
	"ccross@...roid.com" <ccross@...roid.com>,
	"keescook@...omium.org" <keescook@...omium.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"matthew.garrett@...ula.com" <matthew.garrett@...ula.com>
Subject: RE: [PATCH 1/2] efivars: Check max_size only if it is non-zero.

> Some (broken?) EFI implementations return always a MaximumVariableSize of 0,
> check against max_size only if it is non-zero.

The spec doesn't say that zero has any special meaning - so if an implementation
returns max_size == 0 but lets you set a variable to a size > 0, then I don't think
there is a need for parentheses or a "?" in this commit comment.

But if Linux silently accepts such broken EFI, then there is no feedback loop
to let EFI implementations know that they are broken.  In other areas we have
thrown out messages about firmware being broken ... perhaps:

	if (max_size == 0)
		printk_once("Broken EFI implementation is returning MaxVariableSize=0\n");

would help? After all there probably *is* a maximum size - but EFI isn't telling us what it is.

-Tony
--
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/