linux-kernel - [tip: x86/fpu] x86/fpu/signal: Remove the legacy alignment check

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Date:   Wed, 23 Jun 2021 22:08:53 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...e.de>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/fpu] x86/fpu/signal: Remove the legacy alignment check

The following commit has been merged into the x86/fpu branch of tip:

Commit-ID:     9ba589f9cdbd8906465b108bc7ec0fc1519a06d3
Gitweb:        https://git.kernel.org/tip/9ba589f9cdbd8906465b108bc7ec0fc1519a06d3
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Wed, 23 Jun 2021 14:02:26 +02:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Wed, 23 Jun 2021 20:01:55 +02:00

x86/fpu/signal: Remove the legacy alignment check

Checking for the XSTATE buffer being 64-byte aligned, and if not,
deciding just to restore the FXSR state is daft.

If user space provides an unaligned math frame and has the extended state
magic set in the FX software reserved bytes, then it really can keep the
pieces.

If the frame is unaligned and the FX software magic is not set, then
fx_only is already set and the restore will use fxrstor.

Remove it.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20210623121457.184149902@linutronix.de
---
 arch/x86/kernel/fpu/signal.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 42e85c3..8a327c0 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -306,9 +306,6 @@ static int __fpu_restore_sig(void __user *buf, void __user *buf_fx,
 		}
 	}
 
-	if ((unsigned long)buf_fx % 64)
-		fx_only = 1;
-
 	if (!ia32_fxstate) {
 		/*
 		 * Attempt to restore the FPU registers directly from user