Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH v1] genirq/msi: fix crash when handling Multi-MSI | Date | Wed, 19 Jan 2022 01:44:52 +0100 |
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On Tue, Jan 18 2022 at 15:39, Thomas Gleixner wrote: > On Mon, Jan 17 2022 at 11:36, Marc Zyngier wrote: >> On Mon, 17 Jan 2022 10:10:13 +0000, >> Tong Zhang <ztong0001@gmail.com> wrote: >>> pci_msi_domain_check_cap (used by ops->msi_check(domain, info, dev)) >>> msi_domain_prepare_irqs >>> __msi_domain_alloc_irqs >>> msi_domain_alloc_irqs_descs_locked >>> >>> What I am suggesting is commit 0f62d941acf9 changed how this return >>> value is being handled and created a UAF >> >> OK, this makes more sense. >> >> But msi_domain_prepare_irqs() shouldn't fail in this case, and we >> should proceed with the allocation of at least one vector, which isn't >> happening here. >> >> Also, if __msi_domain_alloc_irqs() is supposed to return the number of >> irqs allocated, it isn't doing it consistently. >> >> Thomas, can you shed some light on what is the intended behaviour >> here? > > Let me stare at it.
It's a subtle issue I overlooked. The UAF is due to
err: pci_msi_unmask(entry, msi_multi_mask(entry));
in msi_capability_init() because the core has torn down and freed the entry already.
The proposed patch "fixes" the issue for the PCI/MSI case, but could cause a memory leak for other callers.
Not sure yet what the proper fix is, but that has to wait until tomorrow when brain becomes awake again.
Thanks,
tglx
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