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FROMLIST: android: binder: Don't get mm from task

Browse Source 
(from https://patchwork.kernel.org/patch/9954125/)

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.

Test: ran binderLibTest, throughputtest, interfacetest and
mempressure w/lockdep
Bug: 63926541
Change-Id: Icc661404eb7a4a2ecc5234b1bf8f0104665f9b45
Acked-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Sherry Yang <sherryy@android.com>
This commit is contained in:
Sherry Yang
2017-09-15 21:12:15 -04:00
committed by Amit Pundir
parent e7edd94d11
commit a455dfd674
2 changed files with 12 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
drivers/android/binder_alloc.c
View File

@@ -215,17 +215,13 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
}
}
if (need_mm)
mm = get_task_mm(alloc->tsk);
/* Same as mmget_not_zero() in later kernel versions */
if (need_mm && atomic_inc_not_zero(&alloc->vma_vm_mm->mm_users))
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) {
@@ -718,6 +714,8 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc,
barrier();
alloc->vma = vma;
alloc->vma_vm_mm = vma->vm_mm;
/* Same as mmgrab() in later kernel versions */
atomic_inc(&alloc->vma_vm_mm->mm_count);
return 0;
@@ -793,6 +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",
@@ -887,7 +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);
}
/**
@@ -924,9 +923,10 @@ 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;
/* Same as mmget_not_zero() in later kernel versions */
if (!atomic_inc_not_zero(&alloc->vma_vm_mm->mm_users))
goto err_mmget;
mm = alloc->vma_vm_mm;
if (!down_write_trylock(&mm->mmap_sem))
goto err_down_write_mmap_sem_failed;
}
@@ -962,7 +962,7 @@ 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:
@@ -1001,7 +1001,6 @@ 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);

1
drivers/android/binder_alloc.h
View File

@@ -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;