4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
commit decab0888e6e14e11d53cefa85f8b3d3b45ce73c upstream.
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@xxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20171230211829.679325424@xxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/tlbflush.h | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -345,15 +345,17 @@ static inline void invalidate_user_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();
}
/*