90 lines
3.2 KiB
Diff
90 lines
3.2 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Sat, 30 Dec 2017 22:13:54 +0100
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Subject: [PATCH] x86/mm: Remove preempt_disable/enable() from
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__native_flush_tlb()
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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CVE-2017-5754
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The preempt_disable/enable() pair in __native_flush_tlb() was added in
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commit:
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5cf0791da5c1 ("x86/mm: Disable preemption during CR3 read+write")
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... to protect the UP variant of flush_tlb_mm_range().
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That preempt_disable/enable() pair should have been added to the UP variant
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of flush_tlb_mm_range() instead.
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The UP variant was removed with commit:
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ce4a4e565f52 ("x86/mm: Remove the UP asm/tlbflush.h code, always use the (formerly) SMP code")
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... but the preempt_disable/enable() pair stayed around.
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The latest change to __native_flush_tlb() in commit:
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6fd166aae78c ("x86/mm: Use/Fix PCID to optimize user/kernel switches")
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... added an access to a per CPU variable outside the preempt disabled
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regions, which makes no sense at all. __native_flush_tlb() must always
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be called with at least preemption disabled.
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Remove the preempt_disable/enable() pair and add a WARN_ON_ONCE() to catch
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bad callers independent of the smp_processor_id() debugging.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Cc: <stable@vger.kernel.org>
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Cc: Andy Lutomirski <luto@kernel.org>
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Cc: Borislav Petkov <bp@alien8.de>
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Cc: Dave Hansen <dave.hansen@linux.intel.com>
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Cc: Dominik Brodowski <linux@dominikbrodowski.net>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>
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Cc: Linus Torvalds <torvalds@linuxfoundation.org>
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Cc: Peter Zijlstra <peterz@infradead.org>
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Link: http://lkml.kernel.org/r/20171230211829.679325424@linutronix.de
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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(cherry picked from commit decab0888e6e14e11d53cefa85f8b3d3b45ce73c)
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Signed-off-by: Andy Whitcroft <apw@canonical.com>
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Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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(cherry picked from commit cfcf931c425b60d0092bcb4a4deb1f5d5db0e293)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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arch/x86/include/asm/tlbflush.h | 14 ++++++++------
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1 file changed, 8 insertions(+), 6 deletions(-)
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diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
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index 7a04a1f1ca11..ff6a6d668c32 100644
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--- a/arch/x86/include/asm/tlbflush.h
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+++ b/arch/x86/include/asm/tlbflush.h
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@@ -334,15 +334,17 @@ static inline void invalidate_user_asid(u16 asid)
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*/
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static inline void __native_flush_tlb(void)
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{
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- invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
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/*
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- * If current->mm == NULL then we borrow a mm which may change
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- * during a task switch and therefore we must not be preempted
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- * while we write CR3 back:
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+ * Preemption or interrupts must be disabled to protect the access
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+ * to the per CPU variable and to prevent being preempted between
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+ * read_cr3() and write_cr3().
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*/
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- preempt_disable();
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+ WARN_ON_ONCE(preemptible());
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+
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+ invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
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+
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+ /* If current->mm == NULL then the read_cr3() "borrows" an mm */
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native_write_cr3(__native_read_cr3());
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- preempt_enable();
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}
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/*
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--
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2.14.2
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