linux-kernel - [PATCH 3.10 094/180] ARM: fix PTRACE

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Message-Id: <1471793510-13022-95-git-send-email-w@1wt.eu>
Date:   Sun, 21 Aug 2016 17:30:24 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Russell King <rmk+kernel@...linux.org.uk>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 094/180] ARM: fix PTRACE_SETVFPREGS on SMP systems

From: Russell King <rmk+kernel@...linux.org.uk>

commit e2dfb4b880146bfd4b6aa8e138c0205407cebbaf upstream.

PTRACE_SETVFPREGS fails to properly mark the VFP register set to be
reloaded, because it undoes one of the effects of vfp_flush_hwstate().

Specifically vfp_flush_hwstate() sets thread->vfpstate.hard.cpu to
an invalid CPU number, but vfp_set() overwrites this with the original
CPU number, thereby rendering the hardware state as apparently "valid",
even though the software state is more recent.

Fix this by reverting the previous change.

Cc: <stable@...r.kernel.org>
Fixes: 8130b9d7b9d8 ("ARM: 7308/1: vfp: flush thread hwstate before copying ptrace registers")
Acked-by: Will Deacon <will.deacon@....com>
Tested-by: Simon Marchi <simon.marchi@...csson.com>
Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
Signed-off-by: Willy Tarreau <w@....eu>
---
 arch/arm/kernel/ptrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index 03deeff..4e2110d 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -733,8 +733,8 @@ static int vfp_set(struct task_struct *target,
 	if (ret)
 		return ret;
 
-	vfp_flush_hwstate(thread);
 	thread->vfpstate.hard = new_vfp;
+	vfp_flush_hwstate(thread);
 
 	return 0;
 }
-- 
2.8.0.rc2.1.gbe9624a