netdev - RE: [patch] isdn: make sure strings are null terminated

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Date:	Thu, 24 Nov 2011 12:30:00 -0000
From:	"David Laight" <David.Laight@...LAB.COM>
To:	<wharms@....de>, "Dan Carpenter" <dan.carpenter@...cle.com>
Cc:	"Karsten Keil" <isdn@...ux-pingi.de>, <netdev@...r.kernel.org>,
	<kernel-janitors@...r.kernel.org>
Subject: RE: [patch] isdn: make sure strings are null terminated

 
> >>> +			if (strlen(dioctl.cf_ctrl.msn) >=
sizeof(dioctl.cf_ctrl.msn))
> >>> +				return -EINVAL;
...
> So far i see you do not get a string, you get a structure. And 
> it will hard to validate the element is a useful string.
> I think my (sledgehammer) method is ok here because you
> make sure that all later calls (strcmp,strcpy) will succeed.
> If someone supplies a bad string the later calls will catch 
> by failing to identify and return a proper code from there
> (at least i hope so).
> 
> re,
>  wh

Except that the strlen() can run right off the end
of the structure - and might eventually fault.
You need to use something like strnlen().

	David


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