serial: pch: Fix PCI device refcount leak in pch_request_dma()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: serial: pch: Fix PCI device refcount leak in pch_request_dma() As comment of pci_get_slot() says, it returns a pci_device with its refcount increased. The caller must decrement the reference count by calling pci_dev_put(). Since 'dma_dev' is only used to filter the channel in filter(), we can call pci_dev_put() before exiting from pch_request_dma(). Add the missing pci_dev_put() for the normal and error path.

References

• https://git.kernel.org/stable/c/90ff030ca10b69feeebda1427550ebf9ed2ad868
• https://git.kernel.org/stable/c/56e5a7c5ee3f0dc8978b5df2b1a98a1b060c5e2a
• https://git.kernel.org/stable/c/dfd15c5550b9190d5b0f9bcacb3e6436322f3854
• https://git.kernel.org/stable/c/d165388227aa7e46a9751b90bae6337b5335cdbb
• https://git.kernel.org/stable/c/07f4ca68b0f6bf84b6b391c14b59fd179fcde9c5
• https://git.kernel.org/stable/c/6f7d82380fbeaed3a940efc33c23f0c4bbd0fc02
• https://git.kernel.org/stable/c/4f5d28865c665c9064de631a518f9bc8099d9ce4
• https://git.kernel.org/stable/c/516614a371c26e3334625b4bca19a5362bf658d6
• https://git.kernel.org/stable/c/8be3a7bf773700534a6e8f87f6ed2ed111254be5