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Date: Sat, 1 Mar 2003 20:12:24 +1100
From: Anton Blanchard <anton@samba.org>
To: Andi Kleen <ak@muc.de>
Cc: sfr@canb.auug.org.au, davem@redhat.com, davidm@hpl.hp.com,
       linux-kernel@vger.kernel.org, matthew@wil.cx, ralf@gnu.org,
       schwidefsky@de.ibm.com, torvalds@transmeta.com
Subject: Re: [PATCH][COMPAT] compat_sys_fcntl{,64} 1/9 Generic part
Message-ID: <20030301091224.GE2606@krispykreme>
References: <200302280950.h1S9oZdx014060@supreme.pcug.org.au> <20030228103609.GA29955@averell>
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> Now there used to be some code that did:
> 
> 	if (get_user(a, &userstruct->firstmember) ||
> 	   __get_user(b, &userstruct->secondmember))
> 		return -EFAULT;
> 
> Assuming that the access_ok in get_user for sizeof(firstmember) covers
> secondmember too which doesn't do access_ok in __get_user. This only
> works assuming it should handle 64bit pointers when there is a memory
> hole at the end of the user process space, otherwise it could
> access kernel pages directly after TASK_SIZE. x86-64 has a big enough 
> hole there, i assume sparc64 and ia64 have too, but i don't know 
> about the other 64bit ports.

Yeah there are a bunch of those in the ioctl and syscall translation
code that annoys me. ppc64 is safe too, but its not something we should
rely on.

Anton
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