Re: [PATCH] PCI/PTM: Keep ptm_enable_cnt balanced when pci_enable_ptm() fails

[sashiko-bot@kernel.org]

> Since commit e1092d5e15e6 ("PCI/PTM: Do not enable PTM automatically
> for Root and Switch Upstream Ports"), pci_enable_ptm() takes a
> reference on the device and on each port of the upstream path, and
> pci_disable_ptm() releases them. If pci_enable_ptm() fails, the counts
> can become incorrect in two ways:
> 
> 1. pci_disable_ptm() decrements dev->ptm_enable_cnt without a check.
>    Many drivers ignore the return value of pci_enable_ptm() and call
>    pci_disable_ptm() unconditionally, for example mlx5 and bnxt. If
>    pci_enable_ptm() failed, for example because the upstream port does
>    not support PTM, the count becomes -1 and stays negative after the
>    driver unbinds. Then pcie_ptm_enabled() returns true, and
>    pci_resume_ptm() can enable PTM on the device after a resume,
>    although the upstream path does not support PTM. Before
>    e1092d5e15e6, pci_disable_ptm() did nothing if PTM was not enabled.
> [ ... ]
> Cc: stable@vger.kernel.org
> Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
> Link: https://lore.kernel.org/r/20261102222817.GA983941@bhelgaas
> Link: https://lore.kernel.org/r/20260616141733.1688264-1-vulab@iscas.ac.cn # [1]
> Signed-off-by: Li Yifan <yifan2.li@intel.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261104121457.2108515-1-yifan2.li@intel.com?part=1