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Subject[PATCH] android: binder: Fix a possible data race in binder_alloc_mmap_handler
Date
The write operations to "alloc->buffer" are protected by
the lock on line 679 and 730, but the read operation to
this data on line 712 is not protected by the lock.
Thus, there may exist a data race for "alloc->buffer".

To fix this data race, the read operation to "alloc->buffer"
should be also protected by the lock.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
drivers/android/binder_alloc.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 5a426c877dfb..596acc3a84e4 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -709,7 +709,9 @@ int binder_alloc_mmap_handler(struct binder_alloc *alloc,
goto err_alloc_buf_struct_failed;
}

+ mutex_lock(&binder_alloc_mmap_lock);
buffer->data = alloc->buffer;
+ mutex_unlock(&binder_alloc_mmap_lock);
list_add(&buffer->entry, &alloc->buffers);
buffer->free = 1;
binder_insert_free_buffer(alloc, buffer);
--
2.17.0
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