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

[Laurent Dufour]

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

Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
---
 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