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| author | Andrea Arcangeli <aarcange@redhat.com> | 2016-10-07 17:01:22 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-07 18:46:29 -0700 |
| commit | 6d2329f8872f23e46a19d240930571510ce525eb (patch) | |
| tree | 598cc5a8d764aa497570b359fc1328be5fa105cc /mm/mmap.c | |
| parent | 6213055f2c068b63078649457391ecea9b489ea3 (diff) | |
| download | linux-6d2329f8872f23e46a19d240930571510ce525eb.tar.gz linux-6d2329f8872f23e46a19d240930571510ce525eb.tar.bz2 linux-6d2329f8872f23e46a19d240930571510ce525eb.zip | |
mm: vm_page_prot: update with WRITE_ONCE/READ_ONCE
vma->vm_page_prot is read lockless from the rmap_walk, it may be updated
concurrently and this prevents the risk of reading intermediate values.
Link: http://lkml.kernel.org/r/1474660305-19222-1-git-send-email-aarcange@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Jan Vorlicek <janvorli@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
| -rw-r--r-- | mm/mmap.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index 7a0707a48047..b3b74cc705ae 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -116,13 +116,15 @@ static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags) void vma_set_page_prot(struct vm_area_struct *vma) { unsigned long vm_flags = vma->vm_flags; + pgprot_t vm_page_prot; - vma->vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags); - if (vma_wants_writenotify(vma)) { + vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags); + if (vma_wants_writenotify(vma, vm_page_prot)) { vm_flags &= ~VM_SHARED; - vma->vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, - vm_flags); + vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags); } + /* remove_protection_ptes reads vma->vm_page_prot without mmap_sem */ + WRITE_ONCE(vma->vm_page_prot, vm_page_prot); } /* @@ -1386,7 +1388,7 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg) * to the private version (using protection_map[] without the * VM_SHARED bit). */ -int vma_wants_writenotify(struct vm_area_struct *vma) +int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot) { vm_flags_t vm_flags = vma->vm_flags; const struct vm_operations_struct *vm_ops = vma->vm_ops; @@ -1401,8 +1403,8 @@ int vma_wants_writenotify(struct vm_area_struct *vma) /* The open routine did something to the protections that pgprot_modify * won't preserve? */ - if (pgprot_val(vma->vm_page_prot) != - pgprot_val(vm_pgprot_modify(vma->vm_page_prot, vm_flags))) + if (pgprot_val(vm_page_prot) != + pgprot_val(vm_pgprot_modify(vm_page_prot, vm_flags))) return 0; /* Do we need to track softdirty? */ |