From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Date: Mon, 27 Mar 2006 09:14:34 +0000 (-0800)
Subject: [PATCH] uml: more carefully test whether we are in a system call
X-Git-Tag: v2.6.17-rc1~468
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=81efcd3300754462537ffac60336158b2f773b4e;p=pandora-kernel.git

[PATCH] uml: more carefully test whether we are in a system call

For security reasons, UML in is_syscall() needs to have access to code in
vsyscall-page.  The current implementation grants this access by explicitly
allowing access to vsyscall in access_ok_skas().  With this change,
copy_from_user() may be used to read the code.  Ptrace access to vsyscall-page
for debugging already was implemented in get_user_pages() by mainline.  In
i386, copy_from_user can't access vsyscall-page, but returns EFAULT.

To make UML behave as i386 does, I changed is_syscall to use
access_process_vm(current) to read the code from vsyscall-page.  This doesn't
hurt security, but simplifies the code and prepares implementation of
stub-vmas.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

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