* [PATCH] mm: rmap: fix use-after-free in __put_anon_vma
@ 2014-06-06 11:30 Andrey Ryabinin
2014-06-06 11:56 ` Peter Zijlstra
0 siblings, 1 reply; 6+ messages in thread
From: Andrey Ryabinin @ 2014-06-06 11:30 UTC (permalink / raw)
To: Andrew Morton, Linus Torvalds, Peter Zijlstra
Cc: linux-mm, linux-kernel, dvyukov, koct9i, Andrey Ryabinin, v3.0+
While working address sanitizer for kernel I've discovered use-after-free
bug in __put_anon_vma.
For the last anon_vma, anon_vma->root freed before child anon_vma.
Later in anon_vma_free(anon_vma) we are referencing to already freed anon_vma->root
to check rwsem.
This patch puts freeing of child anon_vma before freeing of anon_vma->root.
Cc: stable@vger.kernel.org # v3.0+
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
---
mm/rmap.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 9c3e773..161bffc7 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1564,10 +1564,11 @@ void __put_anon_vma(struct anon_vma *anon_vma)
{
struct anon_vma *root = anon_vma->root;
- if (root != anon_vma && atomic_dec_and_test(&root->refcount))
+ if (root != anon_vma && atomic_dec_and_test(&root->refcount)) {
+ anon_vma_free(anon_vma);
anon_vma_free(root);
-
- anon_vma_free(anon_vma);
+ } else
+ anon_vma_free(anon_vma);
}
static struct anon_vma *rmap_walk_anon_lock(struct page *page,
--
1.8.5.5
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: rmap: fix use-after-free in __put_anon_vma
2014-06-06 11:30 [PATCH] mm: rmap: fix use-after-free in __put_anon_vma Andrey Ryabinin
@ 2014-06-06 11:56 ` Peter Zijlstra
2014-06-06 14:16 ` Andrey Ryabinin
2014-06-06 15:09 ` [PATCH v2] " Andrey Ryabinin
0 siblings, 2 replies; 6+ messages in thread
From: Peter Zijlstra @ 2014-06-06 11:56 UTC (permalink / raw)
To: Andrey Ryabinin
Cc: Andrew Morton, Linus Torvalds, linux-mm, linux-kernel, dvyukov,
koct9i, v3.0+
[-- Attachment #1: Type: text/plain, Size: 1439 bytes --]
On Fri, Jun 06, 2014 at 03:30:55PM +0400, Andrey Ryabinin wrote:
> While working address sanitizer for kernel I've discovered use-after-free
> bug in __put_anon_vma.
> For the last anon_vma, anon_vma->root freed before child anon_vma.
> Later in anon_vma_free(anon_vma) we are referencing to already freed anon_vma->root
> to check rwsem.
> This patch puts freeing of child anon_vma before freeing of anon_vma->root.
Yes, I think that is right indeed.
Very hard to hit, but valid since not all callers hold rcu_read_lock().
>
> Cc: stable@vger.kernel.org # v3.0+
> Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
> ---
> mm/rmap.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 9c3e773..161bffc7 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1564,10 +1564,11 @@ void __put_anon_vma(struct anon_vma *anon_vma)
> {
> struct anon_vma *root = anon_vma->root;
>
> - if (root != anon_vma && atomic_dec_and_test(&root->refcount))
> + if (root != anon_vma && atomic_dec_and_test(&root->refcount)) {
> + anon_vma_free(anon_vma);
> anon_vma_free(root);
> -
> - anon_vma_free(anon_vma);
> + } else
> + anon_vma_free(anon_vma);
> }
Why not simply move the freeing of anon_vma before the root, like:
anon_vma_free(anon_vma);
if (root != anon_vma && atomic_dec_and_test(&root->refcount))
anon_vma_free(root);
?
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: rmap: fix use-after-free in __put_anon_vma
2014-06-06 11:56 ` Peter Zijlstra
@ 2014-06-06 14:16 ` Andrey Ryabinin
2014-06-06 15:09 ` [PATCH v2] " Andrey Ryabinin
1 sibling, 0 replies; 6+ messages in thread
From: Andrey Ryabinin @ 2014-06-06 14:16 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Andrew Morton, Linus Torvalds, linux-mm, linux-kernel, dvyukov, koct9i
On 06/06/14 15:56, Peter Zijlstra wrote:
> On Fri, Jun 06, 2014 at 03:30:55PM +0400, Andrey Ryabinin wrote:
>> While working address sanitizer for kernel I've discovered use-after-free
>> bug in __put_anon_vma.
>> For the last anon_vma, anon_vma->root freed before child anon_vma.
>> Later in anon_vma_free(anon_vma) we are referencing to already freed anon_vma->root
>> to check rwsem.
>> This patch puts freeing of child anon_vma before freeing of anon_vma->root.
>
> Yes, I think that is right indeed.
>
> Very hard to hit, but valid since not all callers hold rcu_read_lock().
>
>>
>> Cc: stable@vger.kernel.org # v3.0+
>> Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
>> ---
>> mm/rmap.c | 7 ++++---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/rmap.c b/mm/rmap.c
>> index 9c3e773..161bffc7 100644
>> --- a/mm/rmap.c
>> +++ b/mm/rmap.c
>> @@ -1564,10 +1564,11 @@ void __put_anon_vma(struct anon_vma *anon_vma)
>> {
>> struct anon_vma *root = anon_vma->root;
>>
>> - if (root != anon_vma && atomic_dec_and_test(&root->refcount))
>> + if (root != anon_vma && atomic_dec_and_test(&root->refcount)) {
>> + anon_vma_free(anon_vma);
>> anon_vma_free(root);
>> -
>> - anon_vma_free(anon_vma);
>> + } else
>> + anon_vma_free(anon_vma);
>> }
>
> Why not simply move the freeing of anon_vma before the root, like:
>
> anon_vma_free(anon_vma);
> if (root != anon_vma && atomic_dec_and_test(&root->refcount))
> anon_vma_free(root);
>
> ?
>
IMO It looks more logical to decrement root's refcounter before freeing child vma.
In fact I wasn't completely sure that it is safe to do so. But after some digging,
now it looks safe to me.
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^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v2] mm: rmap: fix use-after-free in __put_anon_vma
2014-06-06 11:56 ` Peter Zijlstra
2014-06-06 14:16 ` Andrey Ryabinin
@ 2014-06-06 15:09 ` Andrey Ryabinin
2014-06-06 15:30 ` Peter Zijlstra
2014-06-07 21:50 ` David Rientjes
1 sibling, 2 replies; 6+ messages in thread
From: Andrey Ryabinin @ 2014-06-06 15:09 UTC (permalink / raw)
To: Andrew Morton, Linus Torvalds, Peter Zijlstra
Cc: linux-mm, linux-kernel, koct9i, Andrey Ryabinin, stable
While working address sanitizer for kernel I've discovered use-after-free
bug in __put_anon_vma.
For the last anon_vma, anon_vma->root freed before child anon_vma.
Later in anon_vma_free(anon_vma) we are referencing to already freed anon_vma->root
to check rwsem.
This patch puts freeing of child anon_vma before freeing of anon_vma->root.
Cc: <stable@vger.kernel.org> # v3.0+
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
---
Changes since v1:
- just made it more simple following Peter's suggestion
mm/rmap.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 9c3e773..cb5f70a 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1564,10 +1564,10 @@ void __put_anon_vma(struct anon_vma *anon_vma)
{
struct anon_vma *root = anon_vma->root;
+ anon_vma_free(anon_vma);
+
if (root != anon_vma && atomic_dec_and_test(&root->refcount))
anon_vma_free(root);
-
- anon_vma_free(anon_vma);
}
static struct anon_vma *rmap_walk_anon_lock(struct page *page,
--
1.8.5.5
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] mm: rmap: fix use-after-free in __put_anon_vma
2014-06-06 15:09 ` [PATCH v2] " Andrey Ryabinin
@ 2014-06-06 15:30 ` Peter Zijlstra
2014-06-07 21:50 ` David Rientjes
1 sibling, 0 replies; 6+ messages in thread
From: Peter Zijlstra @ 2014-06-06 15:30 UTC (permalink / raw)
To: Andrey Ryabinin
Cc: Andrew Morton, Linus Torvalds, linux-mm, linux-kernel, koct9i,
stable, Hugh Dickins
On Fri, Jun 06, 2014 at 07:09:30PM +0400, Andrey Ryabinin wrote:
> While working address sanitizer for kernel I've discovered use-after-free
> bug in __put_anon_vma.
> For the last anon_vma, anon_vma->root freed before child anon_vma.
> Later in anon_vma_free(anon_vma) we are referencing to already freed anon_vma->root
> to check rwsem.
> This patch puts freeing of child anon_vma before freeing of anon_vma->root.
>
> Cc: <stable@vger.kernel.org> # v3.0+
Acked-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
> ---
>
> Changes since v1:
> - just made it more simple following Peter's suggestion
>
> mm/rmap.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 9c3e773..cb5f70a 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1564,10 +1564,10 @@ void __put_anon_vma(struct anon_vma *anon_vma)
> {
> struct anon_vma *root = anon_vma->root;
>
> + anon_vma_free(anon_vma);
> +
> if (root != anon_vma && atomic_dec_and_test(&root->refcount))
> anon_vma_free(root);
> -
> - anon_vma_free(anon_vma);
> }
>
> static struct anon_vma *rmap_walk_anon_lock(struct page *page,
> --
> 1.8.5.5
>
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] mm: rmap: fix use-after-free in __put_anon_vma
2014-06-06 15:09 ` [PATCH v2] " Andrey Ryabinin
2014-06-06 15:30 ` Peter Zijlstra
@ 2014-06-07 21:50 ` David Rientjes
1 sibling, 0 replies; 6+ messages in thread
From: David Rientjes @ 2014-06-07 21:50 UTC (permalink / raw)
To: Andrey Ryabinin
Cc: Andrew Morton, Linus Torvalds, Peter Zijlstra, linux-mm,
linux-kernel, koct9i, stable
On Fri, 6 Jun 2014, Andrey Ryabinin wrote:
> While working address sanitizer for kernel I've discovered use-after-free
> bug in __put_anon_vma.
> For the last anon_vma, anon_vma->root freed before child anon_vma.
> Later in anon_vma_free(anon_vma) we are referencing to already freed anon_vma->root
> to check rwsem.
> This patch puts freeing of child anon_vma before freeing of anon_vma->root.
>
> Cc: <stable@vger.kernel.org> # v3.0+
> Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Acked-by: David Rientjes <rientjes@google.com>
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^ permalink raw reply [flat|nested] 6+ messages in thread
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2014-06-06 11:30 [PATCH] mm: rmap: fix use-after-free in __put_anon_vma Andrey Ryabinin
2014-06-06 11:56 ` Peter Zijlstra
2014-06-06 14:16 ` Andrey Ryabinin
2014-06-06 15:09 ` [PATCH v2] " Andrey Ryabinin
2014-06-06 15:30 ` Peter Zijlstra
2014-06-07 21:50 ` David Rientjes
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