From 66e48a0d29bdedc574c8fc0af7a5d112b594ced6 Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Thu, 24 May 2018 15:54:30 +0100 Subject: [PATCH] arm64: fpsimd: Avoid FPSIMD context leakage for the init task MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The init task is started with thread_flags equal to 0, which means that TIF_FOREIGN_FPSTATE is initially clear. It is theoretically possible (if unlikely) that the init task could reach userspace without ever being scheduled out. If this occurs, data left in the FPSIMD registers by the kernel could be exposed. This patch fixes this anomaly by ensuring that the init task's initial TIF_FOREIGN_FPSTATE is set. Signed-off-by: Dave Martin Fixes: 005f78cd8849 ("arm64: defer reloading a task's FPSIMD state to userland resume") Reviewed-by: Catalin Marinas Reviewed-by: Alex Bennée Cc: Will Deacon Cc: Ard Biesheuvel Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/thread_info.h | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 740aa03c5f0d..af271f9a6c9f 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -45,12 +45,6 @@ struct thread_info { int preempt_count; /* 0 => preemptable, <0 => bug */ }; -#define INIT_THREAD_INFO(tsk) \ -{ \ - .preempt_count = INIT_PREEMPT_COUNT, \ - .addr_limit = KERNEL_DS, \ -} - #define thread_saved_pc(tsk) \ ((unsigned long)(tsk->thread.cpu_context.pc)) #define thread_saved_sp(tsk) \ @@ -117,5 +111,12 @@ void arch_release_task_struct(struct task_struct *tsk); _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \ _TIF_NOHZ) +#define INIT_THREAD_INFO(tsk) \ +{ \ + .flags = _TIF_FOREIGN_FPSTATE, \ + .preempt_count = INIT_PREEMPT_COUNT, \ + .addr_limit = KERNEL_DS, \ +} + #endif /* __KERNEL__ */ #endif /* __ASM_THREAD_INFO_H */ -- 2.30.2