x86/vdso: Plug race between mapping and ELF header setup
authorThomas Gleixner <tglx@linutronix.de>
Mon, 10 Apr 2017 15:14:28 +0000 (17:14 +0200)
committerThomas Gleixner <tglx@linutronix.de>
Mon, 10 Apr 2017 16:31:41 +0000 (18:31 +0200)
commit6fdc6dd90272ce7e75d744f71535cfbd8d77da81
treea6c19e22befb56580fd103b4e855ab9567ff69ac
parentc06989da39cdb10604d572c8c7ea8c8c97f3c483
x86/vdso: Plug race between mapping and ELF header setup

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>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20170410151723.602367196@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
arch/x86/include/asm/elf.h