From 146fbd04c86f6898f3b57e6eeb7e26b65f8b82e4 Mon Sep 17 00:00:00 2001
From: Dave Martin <Dave.Martin@arm.com>
Date: Thu, 24 May 2018 15:54:30 +0100
Subject: [PATCH 10/20] arm64: fpsimd: Avoid FPSIMD context leakage for the
init task
Git-commit: 66e48a0d29bdedc574c8fc0af7a5d112b594ced6
Patch-mainline: v4.18-rc1
References: bsc#1106894
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 <Dave.Martin@arm.com>
Fixes: 005f78cd8849 ("arm64: defer reloading a task's FPSIMD state to userland resume")
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
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 f72f809f4765..6fc3df49a1aa 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 init_stack (init_thread_union.stack)
#define thread_saved_pc(tsk) \
@@ -110,5 +104,12 @@ struct thread_info {
_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 */
--
2.11.0