[+cc Jan] On Thu, Oct 06, 2022 at 01:59:50PM +0200, Stephen Kitt wrote: > In pcie_aspm_init_link_state(), a number of checks are made to > determine whether the function should proceed, before the result of > the call to pcie_aspm_sanity_check() is actually used. The latter > function doesn't change any state, it only reports a result, so > calling it later doesn't make any difference to the state of the > devices or the information we have about them. But having the call > early reportedly can cause null-pointer dereferences; see > https://unix.stackexchange.com/q/322337 for one example with > pcie_aspm=off (this was reported in 2016, but the relevant code hasn't > changed since then). Thanks, Stephen! That stackexchange report doesn't have much information, but it looks similar to this old report from Jan Rueth, which I'm sorry to say I never got resolved: https://bugzilla.kernel.org/show_bug.cgi?id=187731 https://lore.kernel.org/all/4cec62c2-218a-672b-8c12-d44e8df56aae@xxxxxxxxxxxxxxxxxxxxx/#t And Jan's patch is almost identical to yours :) I hope to get this resolved, but I don't have time to work on it before the upcoming merge window, which will probably open Sunday. And then it's holiday time, so it may be January before I get back to it. I'm just dropping the links here as breadcrumbs for picking this back up. Bjorn > This moves the call to pcie_aspm_sanity_check() just before the result > is actually used, giving all the other checks a chance to run first. > > Signed-off-by: Stephen Kitt <steve@xxxxxxx> > --- > drivers/pci/pcie/aspm.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c > index a8aec190986c..38df439568b7 100644 > --- a/drivers/pci/pcie/aspm.c > +++ b/drivers/pci/pcie/aspm.c > @@ -889,7 +889,7 @@ static void pcie_aspm_update_sysfs_visibility(struct pci_dev *pdev) > void pcie_aspm_init_link_state(struct pci_dev *pdev) > { > struct pcie_link_state *link; > - int blacklist = !!pcie_aspm_sanity_check(pdev); > + int blacklist; > > if (!aspm_support_enabled) > return; > @@ -923,6 +923,7 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev) > * upstream links also because capable state of them can be > * update through pcie_aspm_cap_init(). > */ > + blacklist = !!pcie_aspm_sanity_check(pdev); > pcie_aspm_cap_init(link, blacklist); > > /* Setup initial Clock PM state */ > > base-commit: 833477fce7a14d43ae4c07f8ddc32fa5119471a2 > -- > 2.30.2 >
