Re: [PATCH] pci: tegra194: Fix debugfs cleanup for !CONFIG_PCIEASPM
From: Hans Zhang
Date: Sat Apr 05 2025 - 11:50:14 EST
On 2025/4/5 23:28, Bjorn Helgaas wrote:
Follow subject line capitalization convention.
On Sat, Apr 05, 2025 at 10:54:59PM +0800, Hans Zhang wrote:
When CONFIG_PCIEASPM is disabled, debugfs entries are not created, but
tegra_pcie_dw_remove() and tegra_pcie_dw_shutdown() unconditionally call
debugfs_remove_recursive(), leading to potential NULL pointer operations.
Introduce deinit_debugfs() to wrap debugfs_remove_recursive(), which is
stubbed for !CONFIG_PCIEASPM. Use this function during removal/shutdown to
ensure debugfs cleanup only occurs when entries were initialized.
This prevents kernel warnings and instability when ASPM support is
disabled.
This looks like there should be a Fixes: tag to connect this to the
commit that introduced the problem.
Hi Bjorn,
Thanks your for reply. Will add.
Fixes: bb617cbd8151 (PCI: tegra194: Clean up the exit path for Endpoint
mode)
If this is something that broke with the v6.15 merge window, we should
include this in v6.15 via pci/for-linus. If this broke earlier, we
would have to decide whether pci/for-linus is still appropriate or a
stable tag.
The original code that introduced the unconditional
`debugfs_remove_recursive()` calls was actually merged in an earlier cycle.
We did merge some debugfs things for v6.15, but I don't see anything
specific to pcie-tegra194.c, so I'm confused about why this fix would
be in pcie-tegra194.c instead of some more generic place.
The Tegra194 driver conditionally initializes pcie->debugfs based on
CONFIG_PCIEASPM. When ASPM is disabled, pcie->debugfs remains
uninitialized, but tegra_pcie_dw_remove() and tegra_pcie_dw_shutdown()
unconditionally call debugfs_remove_recursive(), leading to a NULL
pointer dereference. This is specific to the Tegra194 implementation, as
other drivers or core PCI code may already guard debugfs cleanup against
uninitialized states through different mechanisms.
Best regards,
Hans