Re: [PATCH] dma-buf: acquire name lock before read/write dma_buf.name

From: Guangming Cao <redacted>

Because dma-buf.name can be freed in func: "dma_buf_set_name",
so, we need to acquire lock first before we read/write dma_buf.name
to prevent Use After Free(UAF) issue.

Signed-off-by: Guangming Cao <redacted>
---
  drivers/dma-buf/dma-buf.c | 5 +++++
  1 file changed, 5 insertions(+)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 511fe0d217a0..aebb51b3ff52 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c

@@ -80,7 +80,9 @@ static void dma_buf_release(struct dentry *dentry)
  		dma_resv_fini(dmabuf->resv);
  
  	module_put(dmabuf->owner);
+	spin_lock(&dmabuf->name_lock);
  	kfree(dmabuf->name);
+	spin_unlock(&dmabuf->name_lock);

  	kfree(dmabuf);
  }
  

@@ -1372,6 +1374,8 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
  		if (ret)
  			goto error_unlock;
  
+
+		spin_lock(&dmabuf->name_lock);
  		seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
  				buf_obj->size,
  				buf_obj->file->f_flags, buf_obj->file->f_mode,

@@ -1379,6 +1383,7 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
  				buf_obj->exp_name,
  				file_inode(buf_obj->file)->i_ino,
  				buf_obj->name ?: "");
+		spin_unlock(&dmabuf->name_lock);