From 06cd58aa18f2b24999c52f3812294a345ee0d32b Mon Sep 17 00:00:00 2001
From: Mark Brown <broonie@kernel.org>
Date: Thu, 9 Sep 2021 17:53:56 +0100
Subject: [PATCH] arm64/sve: Use correct size when reinitialising SVE state
Git-commit: e35ac9d0b56e9efefaeeb84b635ea26c2839ea86
Patch-mainline: v5.15-rc2
References: stable-5.14.7

commit e35ac9d0b56e9efefaeeb84b635ea26c2839ea86 upstream.

When we need a buffer for SVE register state we call sve_alloc() to make
sure that one is there. In order to avoid repeated allocations and frees
we keep the buffer around unless we change vector length and just memset()
it to ensure a clean register state. The function that deals with this
takes the task to operate on as an argument, however in the case where we
do a memset() we initialise using the SVE state size for the current task
rather than the task passed as an argument.

This is only an issue in the case where we are setting the register state
for a task via ptrace and the task being configured has a different vector
length to the task tracing it. In the case where the buffer is larger in
the traced process we will leak old state from the traced process to
itself, in the case where the buffer is smaller in the traced process we
will overflow the buffer and corrupt memory.

Fixes: bc0ee4760364 ("arm64/sve: Core task context handling")
Cc: <stable@vger.kernel.org> # 4.15.x
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210909165356.10675-1-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 arch/arm64/kernel/fpsimd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index e57b23f95284..3599b9a2f1df 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -511,7 +511,7 @@ size_t sve_state_size(struct task_struct const *task)
 void sve_alloc(struct task_struct *task)
 {
 	if (task->thread.sve_state) {
-		memset(task->thread.sve_state, 0, sve_state_size(current));
+		memset(task->thread.sve_state, 0, sve_state_size(task));
 		return;
 	}
 
-- 
2.26.2