linux-kernel - Re: [Patch 01/11] Introducing generic hardware breakpoint handler interfaces

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]

Message-ID: <Pine.LNX.4.44L0.0903231514350.3610-100000@iolanthe.rowland.org>
Date:	Mon, 23 Mar 2009 15:21:49 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"K.Prasad" <prasad@...ux.vnet.ibm.com>
cc:	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Benjamin Herrenschmidt <benh@....ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Maneesh Soni <maneesh@...ibm.com>,
	Roland McGrath <roland@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [Patch 01/11] Introducing generic hardware breakpoint handler
 interfaces

On Tue, 24 Mar 2009, K.Prasad wrote:

> > > Ok. Will do something like:
> > > return (va <= (TASK_SIZE - (hw_breakpoint_length * word_size)));
> > 
> > What is the purpose of word_size here?  The breakpoint length should be 
> > specified in bytes, not words.
> > 
> > Don't forget that that in arch_check_va_in_kernelspace() you need to 
> > check both for values that are too low and values that are too high 
> > (they overflow and wrap around back to a user address).
> > 
> 
> While I understand the user-space checking using the length of the HW
> Breakpoint, I don't really see how I can check for an upper-bound for
> kernel-space virtual addresses. Most usage in the kernel only checks for
> the address >= TASK_SIZE (while they check for add + len if the length
> of the memory is known). I will be glad to have any suggestions in this
> regard.

Isn't that exactly the check you need to implement?

	addr >= TASK_SIZE && (addr + len) >= TASK_SIZE,

or perhaps better,

	addr >= TASK_SIZE && (addr + len) >= addr.

In this case you _do_ know the length of the breakpoint.

Alan Stern

--
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/