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Subject[PATCH] android: binder: Sanity check at binder ioctl
Date
When a process fork a child process, we should not allow the
child process use the binder which opened by parent process.

But if the binder-object creater is a thread of one process who exit,
the other thread can also use this binder-object normally.
We can distinguish this by the member proc->tsk->mm.
If the thread exit the tsk->mm will be NULL.

proc->tsk->mm != current->tsk->mm && proc->tsk->mm

So only allow the shared mm_struct to use the same binder-object and
check the existence of mm_struct.

Signed-off-by: Chen Feng <puck.chen@hisilicon.com>
Signed-off-by: Wei Dong <weidong2@hisilicon.com>
Signed-off-by: Junmin Zhao <zhaojunmin@huawei.com>
Reviewed-by: Zhuangluan Su <suzhuangluan@hisilicon.com>
---
drivers/android/binder.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index a39e85f..3a74c5d 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2736,6 +2736,8 @@ static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)

/*pr_info("binder_ioctl: %d:%d %x %lx\n",
proc->pid, current->pid, cmd, arg);*/
+ if (unlikely(proc->tsk->mm != current->tsk->mm && proc->tsk->mm))
+ return -EINVAL;

trace_binder_ioctl(cmd, arg);

--
1.9.1

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