linux-kernel - Re: revert bab65e48cb064 PCI/MSI Sanitize MSI-X checks

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Date:   Thu, 06 Apr 2023 21:46:29 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        David Laight <David.Laight@...LAB.COM>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jason Gunthorpe <jgg@...dia.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Christoph Hellwig <hch@...radead.org>,
        linux-pci@...r.kernel.org, regressions@...ts.linux.dev
Subject: Re: revert bab65e48cb064 PCI/MSI Sanitize MSI-X checks

On Thu, Apr 06 2023 at 10:07, Bjorn Helgaas wrote:
> On Thu, Apr 06, 2023 at 11:05:14AM +0000, David Laight wrote:
> Thanks for the report!  bab65e48cb06 ("PCI/MSI: Sanitize MSI-X
> checks") appeared in v6.2-rc1, so this is a recent regression and it
> would be good to fix it for v6.3.
>
> bab65e48cb06 only touches drivers/pci/msi/msi.c, but since it didn't
> go through the PCI tree, I'll let Thomas handle any revert (or better,
> an improvement to pci_msix_validate_entries()) since he wrote and
> applied the original.

Right. The fix is trivial as the hardware size check in this validation
function is pointless.

The point is that for a range allocation with and entries array, _all_
entries up to max_vec must be correct independent of the actual hardware
size.

So the fix is simply removing the hardware size check from the
validation function.

The hardware size checking happens afterwards anyway.

Thanks,

        tglx
---
 drivers/pci/msi/msi.c |    9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

--- a/drivers/pci/msi/msi.c
+++ b/drivers/pci/msi/msi.c
@@ -750,8 +750,7 @@ static int msix_capability_init(struct p
 	return ret;
 }
 
-static bool pci_msix_validate_entries(struct pci_dev *dev, struct msix_entry *entries,
-				      int nvec, int hwsize)
+static bool pci_msix_validate_entries(struct pci_dev *dev, struct msix_entry *entries, int nvev)
 {
 	bool nogap;
 	int i, j;
@@ -762,10 +761,6 @@ static bool pci_msix_validate_entries(st
 	nogap = pci_msi_domain_supports(dev, MSI_FLAG_MSIX_CONTIGUOUS, DENY_LEGACY);
 
 	for (i = 0; i < nvec; i++) {
-		/* Entry within hardware limit? */
-		if (entries[i].entry >= hwsize)
-			return false;
-
 		/* Check for duplicate entries */
 		for (j = i + 1; j < nvec; j++) {
 			if (entries[i].entry == entries[j].entry)
@@ -805,7 +800,7 @@ int __pci_enable_msix_range(struct pci_d
 	if (hwsize < 0)
 		return hwsize;
 
-	if (!pci_msix_validate_entries(dev, entries, nvec, hwsize))
+	if (!pci_msix_validate_entries(dev, entries, nvec))
 		return -EINVAL;
 
 	if (hwsize < nvec) {