linux-kernel - [RFC v3 16/17] mm: protect madvise vs speculative pf

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Date:   Thu, 27 Apr 2017 17:52:55 +0200
From:   Laurent Dufour <ldufour@...ux.vnet.ibm.com>
To:     paulmck@...ux.vnet.ibm.com, peterz@...radead.org,
        akpm@...ux-foundation.org, kirill@...temov.name,
        ak@...ux.intel.com, mhocko@...nel.org, dave@...olabs.net,
        jack@...e.cz
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        haren@...ux.vnet.ibm.com, khandual@...ux.vnet.ibm.com,
        npiggin@...il.com, bsingharora@...il.com
Subject: [RFC v3 16/17] mm: protect madvise vs speculative pf

This is an attempt to protect madvise's effect against the speculative
page fault handler.

Signed-off-by: Laurent Dufour <ldufour@...ux.vnet.ibm.com>
---
 mm/madvise.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 0e3828eae9f8..f91b64564571 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -132,8 +132,9 @@ static long madvise_behavior(struct vm_area_struct *vma,
 	/*
 	 * vm_flags is protected by the mmap_sem held in write mode.
 	 */
+	write_seqcount_begin(&vma->vm_sequence);
 	vma->vm_flags = new_flags;
-
+	write_seqcount_end(&vma->vm_sequence);
 out:
 	if (error == -ENOMEM)
 		error = -EAGAIN;
@@ -403,9 +404,11 @@ static void madvise_free_page_range(struct mmu_gather *tlb,
 		.private = tlb,
 	};
 
+	write_seqcount_begin(&vma->vm_sequence);
 	tlb_start_vma(tlb, vma);
 	walk_page_range(addr, end, &free_walk);
 	tlb_end_vma(tlb, vma);
+	write_seqcount_end(&vma->vm_sequence);
 }
 
 static int madvise_free_single_vma(struct vm_area_struct *vma,
-- 
2.7.4