linux-kernel - [PATCH] PCI/MSI: Remove over-zealous hardware size check in pci_msix_validate

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Date:   Mon, 10 Apr 2023 21:14:45 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.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>,
        Christoph Hellwig <hch@...radead.org>
Subject: [PATCH] PCI/MSI: Remove over-zealous hardware size check in
 pci_msix_validate_entries()

pci_msix_validate_entries() validates the entries array which is handed in
by the caller for a MSI-X interrupt allocation. Aside of consistency
failures it also detects a failure when the size of the MSI-X hardware table
in the device is smaller than the size of the entries array.

That's wrong for the case of range allocations where the caller provides
the minimum and the maximum number of vectors to allocate, when the
hardware size is greater or equal to the mininum, but smaller than the
maximum.

Remove the hardware size check completely from that function and just
ensure that the entires array up to the maximum size is consistent.

The limitation and range checking versus the hardware size happens
independently of that afterwards anyway because the entries array is
optional.

Fixes: 4644d22eb673 ("PCI/MSI: Validate MSI-X contiguous restriction early")
Reported-by: David Laight <David.Laight@...lab.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---

David, can you please confirm that this fixes your issue?

---
 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) {