Patch "x86/vdso: Plug race between mapping and ELF header setup" has been added to the 4.4-stable tree

Patch "x86/vdso: Plug race between mapping and ELF header setup" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    x86/vdso: Plug race between mapping and ELF header setup

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-vdso-plug-race-between-mapping-and-elf-header-setup.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 6fdc6dd90272ce7e75d744f71535cfbd8d77da81 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 10 Apr 2017 17:14:28 +0200
Subject: x86/vdso: Plug race between mapping and ELF header setup

From: Thomas Gleixner <tglx@linutronix.de>

commit 6fdc6dd90272ce7e75d744f71535cfbd8d77da81 upstream.

The vsyscall32 sysctl can racy against a concurrent fork when it switches
from disabled to enabled:

    arch_setup_additional_pages()
	if (vdso32_enabled)
           --> No mapping
                                        sysctl.vsysscall32()
                                          --> vdso32_enabled = true
    create_elf_tables()
      ARCH_DLINFO_IA32
        if (vdso32_enabled) {
           --> Add VDSO entry with NULL pointer

Make ARCH_DLINFO_IA32 check whether the VDSO mapping has been set up for
the newly forked process or not.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mathias Krause <minipli@googlemail.com>
Link: http://lkml.kernel.org/r/20170410151723.602367196@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/include/asm/elf.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -278,7 +278,7 @@ struct task_struct;
 
 #define	ARCH_DLINFO_IA32						\
 do {									\
-	if (vdso32_enabled) {						\
+	if (VDSO_CURRENT_BASE) {					\
 		NEW_AUX_ENT(AT_SYSINFO,	VDSO_ENTRY);			\
 		NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_CURRENT_BASE);	\
 	}								\


Patches currently in stable-queue which might be from tglx@linutronix.de are

queue-4.4/x86-vdso-ensure-vdso32_enabled-gets-set-to-valid-values-only.patch
queue-4.4/x86-vdso-plug-race-between-mapping-and-elf-header-setup.patch
queue-4.4/cgroup-kthread-close-race-window-where-new-kthreads-can-be-migrated-to-non-root-cgroups.patch
queue-4.4/perf-x86-avoid-exposing-wrong-stale-data-in-intel_pmu_lbr_read_32.patch