linux-kernel - [PATCH 2/2] powerpc/powernv/pci: Fix underflow and leak issue

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Message-Id: <70f8debe8688e0b467367db769b71c20146a836d.1754300646.git.namcao@linutronix.de>
Date: Mon,  4 Aug 2025 12:07:28 +0200
From: Nam Cao <namcao@...utronix.de>
To: Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Gautam Menghani <gautam@...ux.ibm.com>,
	Cédric Le Goater <clg@...d.org>,
	linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org
Cc: Nam Cao <namcao@...utronix.de>,
	stable@...r.kernel.org
Subject: [PATCH 2/2] powerpc/powernv/pci: Fix underflow and leak issue

pnv_irq_domain_alloc() allocates interrupts at parent's interrupt
domain. If it fails in the progress, all allocated interrupts are
freed.

The number of successfully allocated interrupts so far is stored
"i". However, "i - 1" interrupts are freed. This is broken:

    - One interrupt is not be freed

    - If "i" is zero, "i - 1" wraps around

Correct the number of freed interrupts to "i".

Fixes: 0fcfe2247e75 ("powerpc/powernv/pci: Add MSI domains")
Signed-off-by: Nam Cao <namcao@...utronix.de>
Cc: stable@...r.kernel.org
---
 arch/powerpc/platforms/powernv/pci-ioda.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index d8ccf2c9b98a..0166bf39ce1e 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -1854,7 +1854,7 @@ static int pnv_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
 	return 0;
 
 out:
-	irq_domain_free_irqs_parent(domain, virq, i - 1);
+	irq_domain_free_irqs_parent(domain, virq, i);
 	msi_bitmap_free_hwirqs(&phb->msi_bmp, hwirq, nr_irqs);
 	return ret;
 }
-- 
2.39.5