Messages in this thread | | | Date | Tue, 27 Feb 2024 18:24:38 +0100 | From | Greg Kroah-Hartman <> | Subject | Re: CVE-2023-52466: PCI: Avoid potential out-of-bounds read in pci_dev_for_each_resource() |
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On Tue, Feb 27, 2024 at 09:07:44AM -0600, Bjorn Helgaas wrote: > [+cc Mika, author of 09cc90063240] > > On Tue, Feb 27, 2024 at 02:26:26PM +0100, Greg Kroah-Hartman wrote: > > On Tue, Feb 27, 2024 at 02:18:51PM +0100, Carlos López wrote: > > > On 25/2/24 9:16, Greg Kroah-Hartman wrote: > > > > There is no actual issue right now because we have another check > > > > afterwards and the out-of-bounds read is not being performed. In > > > > any case it's better code with this fixed, hence the proposed > > > > change. > > > > > > Given that there is no actual security issue this looks more like a > > > hardening, and thus not deserving of a CVE, no? > > > > This was a tricky one, I think it's needed as we do not know how people > > are really using these macros, right? If the PCI maintainer agrees (on > > the cc:), I'll be glad to revoke it, it's their call. > > 09cc90063240 ("PCI: Introduce pci_dev_for_each_resource()") added > pci_dev_for_each_resource(), which expands to: > > for (...; res = (&(dev)->resource[(bar)]), bar < PCI_NUM_RESOURCES; ...) > > We compute "res" before the bounds-check of "bar", so the pointer may > be out-of-bounds, but the body of the pci_dev_for_each_resource() loop > is never executed with that out-of-bounds value. > > So I don't think this is a security issue, no matter how > pci_dev_for_each_resource() is used, unless the mere presence of an > invalid address in a register is an issue.
Ah, yeah, now I remember, stuff like this was fixed up in other loops as just reading off into the wild can be a speculation issue and so we had to fix up a bunch of places in the kernel where we did have "invalid data" in a register. The code didn't use that, but the processor would fetch from there, and boom, speculation mess. There's a whole research paper published on this type of thing somewhere...
So let's keep this as a CVE unless someone really doesn't want it marked as such. Again, it is a "weakness that is fixed" in the kernel, and because of that, a CVE can be allocated for it.
thanks,
greg k-h
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