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Groups > linux.kernel > #1493669

[tip:x86/urgent] x86/init: Fix cr4_init_shadow() on CR4-less machines

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Commit-ID:  e1bfc11c5a6f40222a698a818dc269113245820e
Gitweb:     http://git.kernel.org/tip/e1bfc11c5a6f40222a698a818dc269113245820e
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Wed, 28 Sep 2016 12:34:14 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 29 Sep 2016 19:08:30 +0200

x86/init: Fix cr4_init_shadow() on CR4-less machines

cr4_init_shadow() will panic on 486-like machines without CR4.  Fix
it using __read_cr4_safe().

Reported-by: david@saggiorato.net
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: 1e02ce4cccdc ("x86: Store a per-cpu shadow copy of CR4")
Link: http://lkml.kernel.org/r/43a20f81fb504013bf613913dc25574b45336a61.1475091074.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/tlbflush.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 6fa8594..dee8a70 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -81,7 +81,7 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate);
 /* Initialize cr4 shadow for this CPU. */
 static inline void cr4_init_shadow(void)
 {
-	this_cpu_write(cpu_tlbstate.cr4, __read_cr4());
+	this_cpu_write(cpu_tlbstate.cr4, __read_cr4_safe());
 }
 
 /* Set in this cpu's CR4. */

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Thread

[PATCH 0/3] CR4 fixes (some are urgent) Andy Lutomirski <luto@kernel.org> - 2016-09-28 21:40 +0200
  [PATCH 2/3] x86/boot: Fix another __read_cr4() case on 486 Andy Lutomirski <luto@kernel.org> - 2016-09-28 21:40 +0200
    Re: [PATCH 2/3] x86/boot: Fix another __read_cr4() case on 486 Borislav Petkov <bp@alien8.de> - 2016-09-29 13:50 +0200
      Re: [PATCH 2/3] x86/boot: Fix another __read_cr4() case on 486 Andy Lutomirski <luto@amacapital.net> - 2016-09-29 21:10 +0200
  [PATCH 3/3] x86/asm: Get rid of __read_cr4_safe() Andy Lutomirski <luto@kernel.org> - 2016-09-28 21:40 +0200
  [PATCH 1/3] x86/init: Fix cr4_init_shadow() on CR4-less machines Andy Lutomirski <luto@kernel.org> - 2016-09-28 21:40 +0200
    Re: [PATCH 1/3] x86/init: Fix cr4_init_shadow() on CR4-less machines Borislav Petkov <bp@alien8.de> - 2016-09-29 13:50 +0200
    [tip:x86/urgent] x86/init: Fix cr4_init_shadow() on CR4-less  machines tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-09-29 20:30 +0200

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