pve-kernel-thunderx/patches/kernel/0220-x86-mm-Remove-preempt_disable-enable-from-__native_f.patch

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From 5a86516e393d12bb3965342f1f690db319d01241 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Sat, 30 Dec 2017 22:13:54 +0100
Subject: [PATCH 220/242] x86/mm: Remove preempt_disable/enable() from
__native_flush_tlb()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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CVE-2017-5754
The preempt_disable/enable() pair in __native_flush_tlb() was added in
commit:
5cf0791da5c1 ("x86/mm: Disable preemption during CR3 read+write")
... to protect the UP variant of flush_tlb_mm_range().
That preempt_disable/enable() pair should have been added to the UP variant
of flush_tlb_mm_range() instead.
The UP variant was removed with commit:
ce4a4e565f52 ("x86/mm: Remove the UP asm/tlbflush.h code, always use the (formerly) SMP code")
... but the preempt_disable/enable() pair stayed around.
The latest change to __native_flush_tlb() in commit:
6fd166aae78c ("x86/mm: Use/Fix PCID to optimize user/kernel switches")
... added an access to a per CPU variable outside the preempt disabled
regions, which makes no sense at all. __native_flush_tlb() must always
be called with at least preemption disabled.
Remove the preempt_disable/enable() pair and add a WARN_ON_ONCE() to catch
bad callers independent of the smp_processor_id() debugging.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linuxfoundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20171230211829.679325424@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit decab0888e6e14e11d53cefa85f8b3d3b45ce73c)
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
(cherry picked from commit cfcf931c425b60d0092bcb4a4deb1f5d5db0e293)
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
---
arch/x86/include/asm/tlbflush.h | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 7a04a1f1ca11..ff6a6d668c32 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -334,15 +334,17 @@ static inline void invalidate_user_asid(u16 asid)
*/
static inline void __native_flush_tlb(void)
{
- invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
/*
- * If current->mm == NULL then we borrow a mm which may change
- * during a task switch and therefore we must not be preempted
- * while we write CR3 back:
+ * Preemption or interrupts must be disabled to protect the access
+ * to the per CPU variable and to prevent being preempted between
+ * read_cr3() and write_cr3().
*/
- preempt_disable();
+ WARN_ON_ONCE(preemptible());
+
+ invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
+
+ /* If current->mm == NULL then the read_cr3() "borrows" an mm */
native_write_cr3(__native_read_cr3());
- preempt_enable();
}
/*
--
2.14.2