dma-buf: fix UAF in dma_buf_put() tracepoint

dma_buf_put() may drop the final file reference via fput(), which
can free the dma-buf. The new tracepoint invocation was added
after fput(), and DMA_BUF_TRACE() dereferences dmabuf and takes
dmabuf->name_lock.

This leads to a use-after-free on the final put, visible for
example as a spinlock bad magic fault on a poisoned 0x6b6b6b...
lock.

Move the dma_buf_put tracepoint before fput().

Reported-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Fixes: 281a22631423 ("dma-buf: add some tracepoints to debug.")
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20260408123916.2604101-1-andi.shyti@kernel.org

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 11711874a325b954940fb289f09936de0152e683..3a9d5113b98c6442e1b2aded6fbcd788899a3705 100644 (file)
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -845,9 +845,8 @@ void dma_buf_put(struct dma_buf *dmabuf)
        if (WARN_ON(!dmabuf || !dmabuf->file))
                return;
 
-       fput(dmabuf->file);
-
        DMA_BUF_TRACE(trace_dma_buf_put, dmabuf);
+       fput(dmabuf->file);
 }
 EXPORT_SYMBOL_NS_GPL(dma_buf_put, "DMA_BUF");