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authorKonstantin Khlebnikov <koct9i@gmail.com>2016-02-05 15:36:50 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-02-25 12:01:21 -0800
commit413aab16bc7b9b58fb1a52010eb3af3d227d7007 (patch)
tree8343d48e64caf80da70535438996c6adb3634c19
parent918a2c388ed7828fa4b6ccb5cacd9e422f30938c (diff)
mm: replace vma_lock_anon_vma with anon_vma_lock_read/write
commit 12352d3cae2cebe18805a91fab34b534d7444231 upstream. 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@mail.gmail.com Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--include/linux/rmap.h14
-rw-r--r--mm/mmap.c55
2 files changed, 25 insertions, 44 deletions
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 29446aeef36e..ddda2ac3446e 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -108,20 +108,6 @@ static inline void put_anon_vma(struct anon_vma *anon_vma)
__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 --git a/mm/mmap.c b/mm/mmap.c
index 2ce04a649f6b..d8cb37af53ac 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -441,12 +441,16 @@ static void validate_mm(struct mm_struct *mm)
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++;
@@ -2147,32 +2151,27 @@ static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, uns
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) {
@@ -2190,7 +2189,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
* 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
@@ -2214,7 +2213,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
}
}
}
- 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;
@@ -2230,25 +2229,21 @@ int expand_downwards(struct vm_area_struct *vma,
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) {
@@ -2266,7 +2261,7 @@ int expand_downwards(struct vm_area_struct *vma,
* 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
@@ -2288,7 +2283,7 @@ int expand_downwards(struct vm_area_struct *vma,
}
}
}
- 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;