[uml-devel] patch uml-host-vdso-fix.patch queued to -stable tree

[<gregkh@suse.de>]

This is a note to let you know that we have just queued up the patch titled

     Subject: UML - host VDSO fix

to the 2.6.20-stable tree.  Its filename is

     uml-host-vdso-fix.patch

A git repo of this tree can be found at 
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary


From stable-bounces@linux.kernel.org Fri Mar 23 12:41:21 2007
From: Jeff Dike <jdike@addtoit.com>
Date: Fri, 23 Mar 2007 15:37:30 -0400
Subject: UML - host VDSO fix
To: stable@kernel.org
Cc: uml-devel <user-mode-linux-devel@lists.sourceforge.net>
Message-ID: <20070323193730.GA9519@c2.user-mode-linux.org>
Content-Disposition: inline

From: Jeff Dike <jdike@addtoit.com>

This fixes a problem seen by a number of people running UML on newer host
kernels.  init would hang with an infinite segfault loop.

It turns out that the host kernel was providing a AT_SYSINFO_EHDR of
0xffffe000, which faked UML into believing that the host VDSO page could be
reused.  However, AT_SYSINFO pointed into the middle of the address space, and
was unmapped as a result.  Because UML was providing AT_SYSINFO_EHDR and
AT_SYSINFO to its own processes, these would branch to nowhere when trying to
use the VDSO.

The fix is to also check the location of AT_SYSINFO when deciding whether to
use the host's VDSO.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

--- linux-2.6.17.orig/arch/um/os-Linux/elf_aux.c	2007-02-23 15:00:51.000000000 -0500
+++ linux-2.6.17/arch/um/os-Linux/elf_aux.c	2007-02-23 15:09:58.000000000 -0500
@@ -39,6 +39,9 @@ __init void scan_elf_aux( char **envp)
 		switch ( auxv->a_type ) {
 			case AT_SYSINFO:
 				__kernel_vsyscall = auxv->a_un.a_val;
+				/* See if the page is under TASK_SIZE */
+				if (__kernel_vsyscall < (unsigned long) envp)
+					__kernel_vsyscall = 0;
 				break;
 			case AT_SYSINFO_EHDR:
 				vsyscall_ehdr = auxv->a_un.a_val;

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Patches currently in stable-queue which might be from jdike@addtoit.com are


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