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

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Am 08.10.21 um 08:29 schrieb guangming.cao@xxxxxxxxxxxx:
From: Guangming Cao <Guangming.Cao@xxxxxxxxxxxx>

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.Cao@xxxxxxxxxxxx>
---
  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);

That here is certainly a NAK. This is the release function if somebody is changing the name on a released DMA-buf we have much bigger problems.

  	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);

Yeah, that part looks like a good idea to me as well.

Christian.

robj = buf_obj->resv;
  		fence = dma_resv_excl_fence(robj);




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