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authorKonstantin Khlebnikov <koct9i@gmail.com>2016-02-05 15:36:50 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-02-05 18:10:40 -0800
commit12352d3cae2cebe18805a91fab34b534d7444231 (patch)
tree07c3e85b4ca5fd3698855c66084fb939727f4f09 /mm/mmap.c
parentc95a51807b730e4681e2ecbdfd669ca52601959e (diff)
downloadlwn-12352d3cae2cebe18805a91fab34b534d7444231.tar.gz
lwn-12352d3cae2cebe18805a91fab34b534d7444231.zip
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@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> Cc: <stable@vger.kernel.org> 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.c55
1 files changed, 25 insertions, 30 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 918c9ec5043f..2f2415a7a688 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -459,12 +459,16 @@ 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++;
@@ -2145,32 +2149,27 @@ 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) {
@@ -2188,7 +2187,7 @@ 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
@@ -2211,7 +2210,7 @@ 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;
@@ -2227,25 +2226,21 @@ 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) {
@@ -2263,7 +2258,7 @@ 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
@@ -2284,7 +2279,7 @@ 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;