| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 20/69] x86/vdso: Plug race between mapping and ELF header setup | Date | Wed, 19 Apr 2017 16:42:36 +0200 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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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); \ } \
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