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[v4,6/6] asm-generic/tlb: avoid potential double flush

Message ID 20200520083025.229011-7-santosh@fossix.org
State New
Headers show
Series Memory corruption may occur due to incorrent tlb flush | expand

Checks

Context Check Description
snowpatch_ozlabs/apply_patch fail Failed to apply to any branch
snowpatch_ozlabs/apply_patch warning Failed to apply on branch linux-next (fb57b1fabcb28f358901b2df90abd2b48abc1ca8)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/fixes (249c9b0cd193d983c3a0b00f3fd3b92333bfeebe)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch linus/master (115a54162a6c0d0ef2aef25ebd0b61fc5e179ebe)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/next (30df74d67d48949da87e3a5b57c381763e8fd526)
snowpatch_ozlabs/apply_patch warning Failed to apply on branch powerpc/merge (7b06fb8795ffea9d12be45a172197c3307955479)

Commit Message

Santosh Sivaraj May 20, 2020, 8:30 a.m. UTC
From: Peter Zijlstra <peterz@infradead.org>

commit 0758cd8304942292e95a0f750c374533db378b32 upstream

Aneesh reported that:

	tlb_flush_mmu()
	  tlb_flush_mmu_tlbonly()
	    tlb_flush()			<-- #1
	  tlb_flush_mmu_free()
	    tlb_table_flush()
	      tlb_table_invalidate()
		tlb_flush_mmu_tlbonly()
		  tlb_flush()		<-- #2

does two TLBIs when tlb->fullmm, because __tlb_reset_range() will not
clear tlb->end in that case.

Observe that any caller to __tlb_adjust_range() also sets at least one of
the tlb->freed_tables || tlb->cleared_p* bits, and those are
unconditionally cleared by __tlb_reset_range().

Change the condition for actually issuing TLBI to having one of those bits
set, as opposed to having tlb->end != 0.

Link: http://lkml.kernel.org/r/20200116064531.483522-4-aneesh.kumar@linux.ibm.com
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reported-by: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: <stable@vger.kernel.org>  # 4.19
Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
[santosh: backported to 4.19 stable]
---
 include/asm-generic/tlb.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index 19934cdd143e..427a70c56ddd 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -179,7 +179,12 @@  static inline void __tlb_reset_range(struct mmu_gather *tlb)
 
 static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
 {
-	if (!tlb->end)
+	/*
+	 * Anything calling __tlb_adjust_range() also sets at least one of
+	 * these bits.
+	 */
+	if (!(tlb->freed_tables || tlb->cleared_ptes || tlb->cleared_pmds ||
+	      tlb->cleared_puds || tlb->cleared_p4ds))
 		return;
 
 	tlb_flush(tlb);