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

[guangming.cao]

From: Guangming Cao <guangming....@mediatek.com>

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 <guangming....@mediatek.com>
---
 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);
 
                robj = buf_obj->resv;
                fence = dma_resv_excl_fence(robj);
-- 
2.17.1