Re: [PATCH v3 9/9] pci: fix UAF when probe runs concurrent to dyn ID removal

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Jul 23, 2026 at 02:29:57PM -0500, Bjorn Helgaas wrote:
> On Thu, Jul 23, 2026 at 07:57:58PM +0100, Gary Guo wrote:
> > On Tue Jul 21, 2026 at 11:35 PM BST, Bjorn Helgaas wrote:
> > > On Mon, Jul 06, 2026 at 03:11:21PM +0100, Gary Guo wrote:
> > >> Dynamic IDs are only guaranteed to be valid when dynids.lock is held,
> > >> as remove_id_store can free the node. Thus, make a copy in
> > >> pci_match_device. Also, clarify that the id parameter is only valid during
> > >> probe.
> > >> 
> > >> Reported-by: Sashiko <sashiko-bot@kernel.org>
> > >> Link: https://lore.kernel.org/all/20260619170503.518F61F00A3A@smtp.kernel.org/
> > >> Fixes: 0994375e9614 ("PCI: add remove_id sysfs entry")
> > >> Signed-off-by: Gary Guo <gary@garyguo.net>
> > >> ---
> > >>  drivers/pci/pci-driver.c | 28 +++++++++++++++-------------
> > >>  include/linux/pci.h      |  1 +
> > >>  2 files changed, 16 insertions(+), 13 deletions(-)
> > >> 
> > >> diff --git a/include/linux/pci.h b/include/linux/pci.h
> > >> index 64b308b6e61c..92c17c116de6 100644
> > >> --- a/include/linux/pci.h
> > >> +++ b/include/linux/pci.h
> > >> @@ -979,6 +979,7 @@ struct module;
> > >>   *		function returns zero when the driver chooses to
> > >>   *		take "ownership" of the device or an error code
> > >>   *		(negative number) otherwise.
> > >> + *		The pci_device_id parameter is only valid during probe.
> > >
> > > The probe function takes a pointer to a struct pci_device_id, so I
> > > think the requirement is that the struct pci_device_id only *needs* to
> > > be valid during .probe(), right, i.e., the PCI core probe path makes
> > > its own copy of the ID and doesn't retain the pointer after .probe()
> > > returns, right?
> > >
> > > I assume the caller determines the struct pci_device_id lifetime, and
> > > it could be forever.
> > >
> > > Could say something like:
> > >
> > >   The pci_device_id parameter only needs to be valid during probe.
> > 
> > As a contract on function parameter, the caller needs to guarantee that it lives
> > at least as long as documented (i.e. during the whole probe) and the callee
> > cannot assume that it will be valid beyond what's guaranteed.
> > 
> > How about:
> > 
> >     The pci_device_id parameter is only guaranteed to be valid during probe.
> 
> That's ok with me.  My only niggle is that this documentation is that the
> *consumer* end, 

I meant to say this documentation is AT the consumer end.

> and of course the consumer, i.e., the PCI core probe path,
> can't guarantee anything about the parameters it receives.  But I guess
> your point is that the *caller* must guarantee that the parameter remains
> valid during probe.
> 
> The only thing the consumer can guarantee is that it doesn't depend on the
> pci_device_id parameter after the probe returns.