[PATCH v2 3/4] uacce: implement mremap in uacce_vm_ops to return -EPERM

[Chenghai Huang <huangchenghai2@huawei.com>]

From: Yang Shen <shenyang39@huawei.com>

The current uacce_vm_ops does not support the mremap operation of
vm_operations_struct. Implement .mremap to return -EPERM to remind
users.

The reason we need to explicitly disable mremap is that when the
driver does not implement .mremap, it uses the default mremap
method. This could lead to a risk scenario:

An application might first mmap address p1, then mremap to p2,
followed by munmap(p1), and finally munmap(p2). Since the default
mremap copies the original vma's vm_private_data (i.e., q) to the
new vma, both munmap operations would trigger vma_close, causing
q->qfr to be freed twice(qfr will be set to null here, so repeated
release is ok).

Fixes: 015d239ac014 ("uacce: add uacce driver")
Cc: stable@vger.kernel.org
Signed-off-by: Yang Shen <shenyang39@huawei.com>
Signed-off-by: Chenghai Huang <huangchenghai2@huawei.com>
---
 drivers/misc/uacce/uacce.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/misc/uacce/uacce.c b/drivers/misc/uacce/uacce.c
index 770a931ef68d..dda71492874d 100644
--- a/drivers/misc/uacce/uacce.c
+++ b/drivers/misc/uacce/uacce.c
@@ -214,8 +214,14 @@ static void uacce_vma_close(struct vm_area_struct *vma)
 	}
 }
 
+static int uacce_vma_mremap(struct vm_area_struct *area)
+{
+	return -EPERM;
+}
+
 static const struct vm_operations_struct uacce_vm_ops = {
 	.close = uacce_vma_close,
+	.mremap = uacce_vma_mremap,
 };
 
 static int uacce_fops_mmap(struct file *filep, struct vm_area_struct *vma)
-- 
2.33.0