linux-kernel - [patch 10/41] x86/fpu: Cleanup arch_set_user_pkey

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Date:   Fri, 11 Jun 2021 18:15:33 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: [patch 10/41] x86/fpu: Cleanup arch_set_user_pkey_access()

The function is having a sanity check with a WARN_ON_ONCE() but happily
proceeds when the pkey argument is out of range.

Clean it up.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/fpu/xstate.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -887,11 +887,10 @@ EXPORT_SYMBOL_GPL(get_xsave_addr);
  * rights for @pkey to @init_val.
  */
 int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
-		unsigned long init_val)
+			      unsigned long init_val)
 {
-	u32 old_pkru;
-	int pkey_shift = (pkey * PKRU_BITS_PER_PKEY);
-	u32 new_pkru_bits = 0;
+	u32 old_pkru, new_pkru_bits = 0;
+	int pkey_shift;
 
 	/*
 	 * This check implies XSAVE support.  OSPKE only gets
@@ -905,7 +904,8 @@ int arch_set_user_pkey_access(struct tas
 	 * values originating from in-kernel users.  Complain
 	 * if a bad value is observed.
 	 */
-	WARN_ON_ONCE(pkey >= arch_max_pkey());
+	if (WARN_ON_ONCE(pkey >= arch_max_pkey()))
+		return -EINVAL;
 
 	/* Set the bits we need in PKRU:  */
 	if (init_val & PKEY_DISABLE_ACCESS)
@@ -914,6 +914,7 @@ int arch_set_user_pkey_access(struct tas
 		new_pkru_bits |= PKRU_WD_BIT;
 
 	/* Shift the bits in to the correct place in PKRU for pkey: */
+	pkey_shift = pkey * PKRU_BITS_PER_PKEY;
 	new_pkru_bits <<= pkey_shift;
 
 	/* Get old PKRU and mask off any old bits in place: */