| 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: [PATCH] x86/vdso: Plug race between mapping and ELF header setup |
| |
| 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> |
| Cc: stable@vger.kernel.org |
| Link: http://lkml.kernel.org/r/20170410151723.602367196@linutronix.de |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| |
| diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h |
| index 9d49c18b5ea9..3762536619f8 100644 |
| --- a/arch/x86/include/asm/elf.h |
| +++ b/arch/x86/include/asm/elf.h |
| @@ -287,7 +287,7 @@ 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); \ |
| } \ |
| -- |
| 2.12.0 |
| |