The patch titled
Subject: mm: replace vma_lock_anon_vma with anon_vma_lock_read/write
has been added to the -mm tree. Its filename is
mm-replace-vma_lock_anon_vma-with-anon_vma_lock_read-write.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-replace-vma_lock_anon_vma-with-anon_vma_lock_read-write.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-replace-vma_lock_anon_vma-with-anon_vma_lock_read-write.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
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------------------------------------------------------
From: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Subject: mm: replace vma_lock_anon_vma with anon_vma_lock_read/write
Sequence vma_lock_anon_vma() - vma_unlock_anon_vma() isn't safe if
anon_vma appeared between lock and unlock. We have to check anon_vma
first or call anon_vma_prepare() to be sure that it's here. There are
only few users of these legacy helpers. Let's get rid of them.
This patch fixes anon_vma lock imbalance in validate_mm(). Write lock
isn't required here, read lock is enough.
And reorders expand_downwards/expand_upwards: security_mmap_addr() and
wrapping-around check don't have to be under anon vma lock.
Link: https://lkml.kernel.org/r/CACT4Y+Y908EjM2z=706dv4rV6dWtxTLK9nFg9_7DhRMLppBo2g@xxxxxxxxxxxxxx
Signed-off-by: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/rmap.h | 14 ----------
mm/mmap.c | 55 ++++++++++++++++++-----------------------
2 files changed, 25 insertions(+), 44 deletions(-)
diff -puN include/linux/rmap.h~mm-replace-vma_lock_anon_vma-with-anon_vma_lock_read-write include/linux/rmap.h
--- a/include/linux/rmap.h~mm-replace-vma_lock_anon_vma-with-anon_vma_lock_read-write
+++ a/include/linux/rmap.h
@@ -109,20 +109,6 @@ static inline void put_anon_vma(struct a
__put_anon_vma(anon_vma);
}
-static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
-{
- struct anon_vma *anon_vma = vma->anon_vma;
- if (anon_vma)
- down_write(&anon_vma->root->rwsem);
-}
-
-static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
-{
- struct anon_vma *anon_vma = vma->anon_vma;
- if (anon_vma)
- up_write(&anon_vma->root->rwsem);
-}
-
static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
{
down_write(&anon_vma->root->rwsem);
diff -puN mm/mmap.c~mm-replace-vma_lock_anon_vma-with-anon_vma_lock_read-write mm/mmap.c
--- a/mm/mmap.c~mm-replace-vma_lock_anon_vma-with-anon_vma_lock_read-write
+++ a/mm/mmap.c
@@ -459,12 +459,16 @@ static void validate_mm(struct mm_struct
struct vm_area_struct *vma = mm->mmap;
while (vma) {
+ struct anon_vma *anon_vma = vma->anon_vma;
struct anon_vma_chain *avc;
- vma_lock_anon_vma(vma);
- list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
- anon_vma_interval_tree_verify(avc);
- vma_unlock_anon_vma(vma);
+ if (anon_vma) {
+ anon_vma_lock_read(anon_vma);
+ list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
+ anon_vma_interval_tree_verify(avc);
+ anon_vma_unlock_read(anon_vma);
+ }
+
highest_address = vma->vm_end;
vma = vma->vm_next;
i++;
@@ -2145,32 +2149,27 @@ static int acct_stack_growth(struct vm_a
int expand_upwards(struct vm_area_struct *vma, unsigned long address)
{
struct mm_struct *mm = vma->vm_mm;
- int error;
+ int error = 0;
if (!(vma->vm_flags & VM_GROWSUP))
return -EFAULT;
- /*
- * We must make sure the anon_vma is allocated
- * so that the anon_vma locking is not a noop.
- */
+ /* Guard against wrapping around to address 0. */
+ if (address < PAGE_ALIGN(address+4))
+ address = PAGE_ALIGN(address+4);
+ else
+ return -ENOMEM;
+
+ /* We must make sure the anon_vma is allocated. */
if (unlikely(anon_vma_prepare(vma)))
return -ENOMEM;
- vma_lock_anon_vma(vma);
/*
* vma->vm_start/vm_end cannot change under us because the caller
* is required to hold the mmap_sem in read mode. We need the
* anon_vma lock to serialize against concurrent expand_stacks.
- * Also guard against wrapping around to address 0.
*/
- if (address < PAGE_ALIGN(address+4))
- address = PAGE_ALIGN(address+4);
- else {
- vma_unlock_anon_vma(vma);
- return -ENOMEM;
- }
- error = 0;
+ anon_vma_lock_write(vma->anon_vma);
/* Somebody else might have raced and expanded it already */
if (address > vma->vm_end) {
@@ -2188,7 +2187,7 @@ int expand_upwards(struct vm_area_struct
* updates, but we only hold a shared mmap_sem
* lock here, so we need to protect against
* concurrent vma expansions.
- * vma_lock_anon_vma() doesn't help here, as
+ * anon_vma_lock_write() doesn't help here, as
* we don't guarantee that all growable vmas
* in a mm share the same root anon vma.
* So, we reuse mm->page_table_lock to guard
@@ -2211,7 +2210,7 @@ int expand_upwards(struct vm_area_struct
}
}
}
- vma_unlock_anon_vma(vma);
+ anon_vma_unlock_write(vma->anon_vma);
khugepaged_enter_vma_merge(vma, vma->vm_flags);
validate_mm(mm);
return error;
@@ -2227,25 +2226,21 @@ int expand_downwards(struct vm_area_stru
struct mm_struct *mm = vma->vm_mm;
int error;
- /*
- * We must make sure the anon_vma is allocated
- * so that the anon_vma locking is not a noop.
- */
- if (unlikely(anon_vma_prepare(vma)))
- return -ENOMEM;
-
address &= PAGE_MASK;
error = security_mmap_addr(address);
if (error)
return error;
- vma_lock_anon_vma(vma);
+ /* We must make sure the anon_vma is allocated. */
+ if (unlikely(anon_vma_prepare(vma)))
+ return -ENOMEM;
/*
* vma->vm_start/vm_end cannot change under us because the caller
* is required to hold the mmap_sem in read mode. We need the
* anon_vma lock to serialize against concurrent expand_stacks.
*/
+ anon_vma_lock_write(vma->anon_vma);
/* Somebody else might have raced and expanded it already */
if (address < vma->vm_start) {
@@ -2263,7 +2258,7 @@ int expand_downwards(struct vm_area_stru
* updates, but we only hold a shared mmap_sem
* lock here, so we need to protect against
* concurrent vma expansions.
- * vma_lock_anon_vma() doesn't help here, as
+ * anon_vma_lock_write() doesn't help here, as
* we don't guarantee that all growable vmas
* in a mm share the same root anon vma.
* So, we reuse mm->page_table_lock to guard
@@ -2284,7 +2279,7 @@ int expand_downwards(struct vm_area_stru
}
}
}
- vma_unlock_anon_vma(vma);
+ anon_vma_unlock_write(vma->anon_vma);
khugepaged_enter_vma_merge(vma, vma->vm_flags);
validate_mm(mm);
return error;
_
Patches currently in -mm which might be from koct9i@xxxxxxxxx are
mm-warn-about-vmdata-over-rlimit_data.patch
mm-polish-virtual-memory-accounting.patch
mm-replace-vma_lock_anon_vma-with-anon_vma_lock_read-write.patch
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