[tip: x86/fpu] x86/fpu: Cleanup arch_set_user_pkey_access()

[tip-bot2 for Thomas Gleixner]

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

Commit-ID:     9fe8a6f5eed8fff6b2d7dbc99b911334e311732d
Gitweb:        https://git.kernel.org/tip/9fe8a6f5eed8fff6b2d7dbc99b911334e311732d
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Wed, 23 Jun 2021 14:01:50 +02:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Wed, 23 Jun 2021 17:52:41 +02:00

x86/fpu: Cleanup arch_set_user_pkey_access()

The function does 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@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lkml.kernel.org/r/20210623121453.635764326@xxxxxxxxxxxxx
---
 arch/x86/kernel/fpu/xstate.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 185cc5d..579e343 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -912,11 +912,10 @@ 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
@@ -930,7 +929,8 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 	 * 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)
@@ -939,6 +939,7 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 		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: */