[PATCH v2 0/4] android: binder: fixes for memory allocator change

[PATCH v2 0/4] android: binder: fixes for memory allocator change

[Sherry Yang]

This patchset resolves a potential deadlock between lru lock, task lock
and dentry lock reported by lockdep. It also fixes the null pointer
dereference in kernel debug message in binder_alloc.c.

Unused vma argument is removed, and binder shrinker is made static.

   android: binder: Don't get mm from task
   android: binder: Fix null ptr dereference in debug msg
   android: binder: Remove unused vma argument
   android: binder: Change binder_shrinker to static

v2: combines the version 1 of two separate patches and reorder
the commits so that the first two can be applied to 4.14.

drivers/android/binder_alloc.c | 40 +++++++++++++++++-----------------------
drivers/android/binder_alloc.h |  1 -
2 files changed, 17 insertions(+), 24 deletions(-)

[PATCH v2 1/4] android: binder: Don't get mm from task

[Sherry Yang]

Use binder_alloc struct's mm_struct rather than getting
a reference to the mm struct through get_task_mm to
avoid a potential deadlock between lru lock, task lock and
dentry lock, since a thread can be holding the task lock
and the dentry lock while trying to acquire the lru lock.

Acked-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Sherry Yang <sherryy@android.com>
---
 drivers/android/binder_alloc.c | 22 +++++++++-------------
 drivers/android/binder_alloc.h |  1 -
 2 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 064f5e31ec55..e12072b1d507 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -215,17 +215,12 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
 		}
 	}
 
-	if (!vma && need_mm)
-		mm = get_task_mm(alloc->tsk);
+	if (!vma && need_mm && mmget_not_zero(alloc->vma_vm_mm))
+		mm = alloc->vma_vm_mm;
 
 	if (mm) {
 		down_write(&mm->mmap_sem);
 		vma = alloc->vma;
-		if (vma && mm != alloc->vma_vm_mm) {
-			pr_err("%d: vma mm and task mm mismatch\n",
-				alloc->pid);
-			vma = NULL;
-		}
 	}
 
 	if (!vma && need_mm) {
@@ -720,6 +715,7 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc,
 	barrier();
 	alloc->vma = vma;
 	alloc->vma_vm_mm = vma->vm_mm;
+	mmgrab(alloc->vma_vm_mm);
 
 	return 0;
 
@@ -795,6 +791,8 @@ void binder_alloc_deferred_release(struct binder_alloc *alloc)
 		vfree(alloc->buffer);
 	}
 	mutex_unlock(&alloc->mutex);
+	if (alloc->vma_vm_mm)
+		mmdrop(alloc->vma_vm_mm);
 
 	binder_alloc_debug(BINDER_DEBUG_OPEN_CLOSE,
 		     "%s: %d buffers %d, pages %d\n",
@@ -889,7 +887,6 @@ int binder_alloc_get_allocated_count(struct binder_alloc *alloc)
 void binder_alloc_vma_close(struct binder_alloc *alloc)
 {
 	WRITE_ONCE(alloc->vma, NULL);
-	WRITE_ONCE(alloc->vma_vm_mm, NULL);
 }
 
 /**
@@ -926,9 +923,9 @@ enum lru_status binder_alloc_free_page(struct list_head *item,
 	page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE;
 	vma = alloc->vma;
 	if (vma) {
-		mm = get_task_mm(alloc->tsk);
-		if (!mm)
-			goto err_get_task_mm_failed;
+		if (!mmget_not_zero(alloc->vma_vm_mm))
+			goto err_mmget;
+		mm = alloc->vma_vm_mm;
 		if (!down_write_trylock(&mm->mmap_sem))
 			goto err_down_write_mmap_sem_failed;
 	}
@@ -963,7 +960,7 @@ enum lru_status binder_alloc_free_page(struct list_head *item,
 
 err_down_write_mmap_sem_failed:
 	mmput_async(mm);
-err_get_task_mm_failed:
+err_mmget:
 err_page_already_freed:
 	mutex_unlock(&alloc->mutex);
 err_get_alloc_mutex_failed:
@@ -1002,7 +999,6 @@ struct shrinker binder_shrinker = {
  */
 void binder_alloc_init(struct binder_alloc *alloc)
 {
-	alloc->tsk = current->group_leader;
 	alloc->pid = current->group_leader->pid;
 	mutex_init(&alloc->mutex);
 	INIT_LIST_HEAD(&alloc->buffers);
diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h
index a3a3602c689c..2dd33b6df104 100644
--- a/drivers/android/binder_alloc.h
+++ b/drivers/android/binder_alloc.h
@@ -100,7 +100,6 @@ struct binder_lru_page {
  */
 struct binder_alloc {
 	struct mutex mutex;
-	struct task_struct *tsk;
 	struct vm_area_struct *vma;
 	struct mm_struct *vma_vm_mm;
 	void *buffer;
-- 
2.11.0 (Apple Git-81)

[PATCH v2 2/4] android: binder: Fix null ptr dereference in debug msg

[Sherry Yang]

Don't access next->data in kernel debug message when the
next buffer is null.

Acked-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Sherry Yang <sherryy@android.com>
---
 drivers/android/binder_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index e12072b1d507..c2819a3d58a6 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -560,7 +560,7 @@ static void binder_delete_free_buffer(struct binder_alloc *alloc,
 		binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
 				   "%d: merge free, buffer %pK do not share page with %pK or %pK\n",
 				   alloc->pid, buffer->data,
-				   prev->data, next->data);
+				   prev->data, next ? next->data : NULL);
 		binder_update_page_range(alloc, 0, buffer_start_page(buffer),
 					 buffer_start_page(buffer) + PAGE_SIZE,
 					 NULL);
-- 
2.11.0 (Apple Git-81)

[PATCH v2 3/4] android: binder: Remove unused vma argument

[Sherry Yang]

The vma argument in update_page_range is no longer
used after 74310e06 ("android: binder: Move buffer
out of area shared with user space"), since mmap_handler
no longer calls update_page_range with a vma.

Acked-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Sherry Yang <sherryy@android.com>
---
 drivers/android/binder_alloc.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index c2819a3d58a6..36bcea1fc47c 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -186,12 +186,12 @@ struct binder_buffer *binder_alloc_prepare_to_free(struct binder_alloc *alloc,
 }
 
 static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
-				    void *start, void *end,
-				    struct vm_area_struct *vma)
+				    void *start, void *end)
 {
 	void *page_addr;
 	unsigned long user_page_addr;
 	struct binder_lru_page *page;
+	struct vm_area_struct *vma = NULL;
 	struct mm_struct *mm = NULL;
 	bool need_mm = false;
 
@@ -215,7 +215,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
 		}
 	}
 
-	if (!vma && need_mm && mmget_not_zero(alloc->vma_vm_mm))
+	if (need_mm && mmget_not_zero(alloc->vma_vm_mm))
 		mm = alloc->vma_vm_mm;
 
 	if (mm) {
@@ -437,7 +437,7 @@ struct binder_buffer *binder_alloc_new_buf_locked(struct binder_alloc *alloc,
 	if (end_page_addr > has_page_addr)
 		end_page_addr = has_page_addr;
 	ret = binder_update_page_range(alloc, 1,
-	    (void *)PAGE_ALIGN((uintptr_t)buffer->data), end_page_addr, NULL);
+	    (void *)PAGE_ALIGN((uintptr_t)buffer->data), end_page_addr);
 	if (ret)
 		return ERR_PTR(ret);
 
@@ -478,7 +478,7 @@ struct binder_buffer *binder_alloc_new_buf_locked(struct binder_alloc *alloc,
 err_alloc_buf_struct_failed:
 	binder_update_page_range(alloc, 0,
 				 (void *)PAGE_ALIGN((uintptr_t)buffer->data),
-				 end_page_addr, NULL);
+				 end_page_addr);
 	return ERR_PTR(-ENOMEM);
 }
 
@@ -562,8 +562,7 @@ static void binder_delete_free_buffer(struct binder_alloc *alloc,
 				   alloc->pid, buffer->data,
 				   prev->data, next ? next->data : NULL);
 		binder_update_page_range(alloc, 0, buffer_start_page(buffer),
-					 buffer_start_page(buffer) + PAGE_SIZE,
-					 NULL);
+					 buffer_start_page(buffer) + PAGE_SIZE);
 	}
 	list_del(&buffer->entry);
 	kfree(buffer);
@@ -600,8 +599,7 @@ static void binder_free_buf_locked(struct binder_alloc *alloc,
 
 	binder_update_page_range(alloc, 0,
 		(void *)PAGE_ALIGN((uintptr_t)buffer->data),
-		(void *)(((uintptr_t)buffer->data + buffer_size) & PAGE_MASK),
-		NULL);
+		(void *)(((uintptr_t)buffer->data + buffer_size) & PAGE_MASK));
 
 	rb_erase(&buffer->rb_node, &alloc->allocated_buffers);
 	buffer->free = 1;
-- 
2.11.0 (Apple Git-81)

[PATCH v2 4/4] android: binder: Change binder_shrinker to static

[Sherry Yang]

binder_shrinker struct is not used anywhere outside of
binder_alloc.c and should be static.

Acked-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Sherry Yang <sherryy@android.com>
---
 drivers/android/binder_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 36bcea1fc47c..6f6f745605af 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -982,7 +982,7 @@ binder_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 	return ret;
 }
 
-struct shrinker binder_shrinker = {
+static struct shrinker binder_shrinker = {
 	.count_objects = binder_shrink_count,
 	.scan_objects = binder_shrink_scan,
 	.seeks = DEFAULT_SEEKS,
-- 
2.11.0 (Apple Git-81)

Re: [PATCH v2 1/4] android: binder: Don't get mm from task

[Greg Kroah-Hartman]

On Fri, Oct 20, 2017 at 08:58:58PM -0400, Sherry Yang wrote:
> Use binder_alloc struct's mm_struct rather than getting
> a reference to the mm struct through get_task_mm to
> avoid a potential deadlock between lru lock, task lock and
> dentry lock, since a thread can be holding the task lock
> and the dentry lock while trying to acquire the lru lock.
> 
> Acked-by: Arve Hjønnevåg <arve@android.com>
> Signed-off-by: Sherry Yang <sherryy@android.com>
> ---
>  drivers/android/binder_alloc.c | 22 +++++++++-------------
>  drivers/android/binder_alloc.h |  1 -
>  2 files changed, 9 insertions(+), 14 deletions(-)

I've applied these first 2 patches, but patches 3 and 4 I have already
applied to my char-misc-next tree, right?

thanks,

greg k-h

Re: [PATCH v2 1/4] android: binder: Don't get mm from task

[Arve Hjønnevåg]

On Sat, Oct 21, 2017 at 1:15 AM, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> On Fri, Oct 20, 2017 at 08:58:58PM -0400, Sherry Yang wrote:
>> Use binder_alloc struct's mm_struct rather than getting
>> a reference to the mm struct through get_task_mm to
>> avoid a potential deadlock between lru lock, task lock and
>> dentry lock, since a thread can be holding the task lock
>> and the dentry lock while trying to acquire the lru lock.
>>
>> Acked-by: Arve Hjønnevåg <arve@android.com>
>> Signed-off-by: Sherry Yang <sherryy@android.com>
>> ---
>>  drivers/android/binder_alloc.c | 22 +++++++++-------------
>>  drivers/android/binder_alloc.h |  1 -
>>  2 files changed, 9 insertions(+), 14 deletions(-)
>
> I've applied these first 2 patches, but patches 3 and 4 I have already
> applied to my char-misc-next tree, right?
>
> thanks,
>
> greg k-h

I would expect you got a merge conflict from one of those. Using patch
3 and 4 in from this patchset should avoid that conflict if your
eventual 4.15 branch is not based on your current char-misc-next
branch.

-- 
Arve Hjønnevåg

Re: [PATCH v2 1/4] android: binder: Don't get mm from task

[Greg Kroah-Hartman]

On Mon, Oct 23, 2017 at 11:18:52AM -0700, Arve Hjønnevåg wrote:
> On Sat, Oct 21, 2017 at 1:15 AM, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > On Fri, Oct 20, 2017 at 08:58:58PM -0400, Sherry Yang wrote:
> >> Use binder_alloc struct's mm_struct rather than getting
> >> a reference to the mm struct through get_task_mm to
> >> avoid a potential deadlock between lru lock, task lock and
> >> dentry lock, since a thread can be holding the task lock
> >> and the dentry lock while trying to acquire the lru lock.
> >>
> >> Acked-by: Arve Hjønnevåg <arve@android.com>
> >> Signed-off-by: Sherry Yang <sherryy@android.com>
> >> ---
> >>  drivers/android/binder_alloc.c | 22 +++++++++-------------
> >>  drivers/android/binder_alloc.h |  1 -
> >>  2 files changed, 9 insertions(+), 14 deletions(-)
> >
> > I've applied these first 2 patches, but patches 3 and 4 I have already
> > applied to my char-misc-next tree, right?
> >
> > thanks,
> >
> > greg k-h
> 
> I would expect you got a merge conflict from one of those. Using patch
> 3 and 4 in from this patchset should avoid that conflict if your
> eventual 4.15 branch is not based on your current char-misc-next
> branch.

I've resolved the merge conflict so my char-misc-next branch should be
all caught up now.  It would be wonderful if you could verify this.

thanks,

greg k-h

Re: [PATCH v2 1/4] android: binder: Don't get mm from task

[Arve Hjønnevåg]

On Tue, Oct 24, 2017 at 12:28 AM, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> On Mon, Oct 23, 2017 at 11:18:52AM -0700, Arve Hjønnevåg wrote:
>> On Sat, Oct 21, 2017 at 1:15 AM, Greg Kroah-Hartman
>> <gregkh@linuxfoundation.org> wrote:
>> > On Fri, Oct 20, 2017 at 08:58:58PM -0400, Sherry Yang wrote:
>> >> Use binder_alloc struct's mm_struct rather than getting
>> >> a reference to the mm struct through get_task_mm to
>> >> avoid a potential deadlock between lru lock, task lock and
>> >> dentry lock, since a thread can be holding the task lock
>> >> and the dentry lock while trying to acquire the lru lock.
>> >>
>> >> Acked-by: Arve Hjønnevåg <arve@android.com>
>> >> Signed-off-by: Sherry Yang <sherryy@android.com>
>> >> ---
>> >>  drivers/android/binder_alloc.c | 22 +++++++++-------------
>> >>  drivers/android/binder_alloc.h |  1 -
>> >>  2 files changed, 9 insertions(+), 14 deletions(-)
>> >
>> > I've applied these first 2 patches, but patches 3 and 4 I have already
>> > applied to my char-misc-next tree, right?
>> >
>> > thanks,
>> >
>> > greg k-h
>>
>> I would expect you got a merge conflict from one of those. Using patch
>> 3 and 4 in from this patchset should avoid that conflict if your
>> eventual 4.15 branch is not based on your current char-misc-next
>> branch.
>
> I've resolved the merge conflict so my char-misc-next branch should be
> all caught up now.  It would be wonderful if you could verify this.
>
> thanks,
>
> greg k-h

I have not tested your branch directly, but the relevant code in
char-misc-next is now identical to the code I tested.

-- 
Arve Hjønnevåg

Re: [PATCH v2 1/4] android: binder: Don't get mm from task

[Greg Kroah-Hartman]

On Tue, Oct 24, 2017 at 11:36:48AM -0700, Arve Hjønnevåg wrote:
> On Tue, Oct 24, 2017 at 12:28 AM, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > On Mon, Oct 23, 2017 at 11:18:52AM -0700, Arve Hjønnevåg wrote:
> >> On Sat, Oct 21, 2017 at 1:15 AM, Greg Kroah-Hartman
> >> <gregkh@linuxfoundation.org> wrote:
> >> > On Fri, Oct 20, 2017 at 08:58:58PM -0400, Sherry Yang wrote:
> >> >> Use binder_alloc struct's mm_struct rather than getting
> >> >> a reference to the mm struct through get_task_mm to
> >> >> avoid a potential deadlock between lru lock, task lock and
> >> >> dentry lock, since a thread can be holding the task lock
> >> >> and the dentry lock while trying to acquire the lru lock.
> >> >>
> >> >> Acked-by: Arve Hjønnevåg <arve@android.com>
> >> >> Signed-off-by: Sherry Yang <sherryy@android.com>
> >> >> ---
> >> >>  drivers/android/binder_alloc.c | 22 +++++++++-------------
> >> >>  drivers/android/binder_alloc.h |  1 -
> >> >>  2 files changed, 9 insertions(+), 14 deletions(-)
> >> >
> >> > I've applied these first 2 patches, but patches 3 and 4 I have already
> >> > applied to my char-misc-next tree, right?
> >> >
> >> > thanks,
> >> >
> >> > greg k-h
> >>
> >> I would expect you got a merge conflict from one of those. Using patch
> >> 3 and 4 in from this patchset should avoid that conflict if your
> >> eventual 4.15 branch is not based on your current char-misc-next
> >> branch.
> >
> > I've resolved the merge conflict so my char-misc-next branch should be
> > all caught up now.  It would be wonderful if you could verify this.
> >
> > thanks,
> >
> > greg k-h
> 
> I have not tested your branch directly, but the relevant code in
> char-misc-next is now identical to the code I tested.

Wonderful, thanks for verifying.

greg k-h