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([2402:f000:4:1006:809:0:a77:18ea]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-34f5fa93ee7sm9124515a91.7.2026.01.08.19.39.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Jan 2026 19:39:17 -0800 (PST) From: Tuo Li To: rafael@kernel.org, lenb@kernel.org Cc: linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, Tuo Li Subject: [PATCH v2] ACPI: processor: Fix a possible null-pointer dereference in acpi_processor_errata_piix4() when debug messages are enabled Date: Fri, 9 Jan 2026 11:38:59 +0800 Message-ID: <20260109033859.187086-1-islituo@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In acpi_processor_errata_piix4(), the pointer dev is first assigned an IDE device and then reassigned an ISA device: dev =3D pci_get_subsys(..., PCI_DEVICE_ID_INTEL_82371AB, ...); dev =3D pci_get_subsys(..., PCI_DEVICE_ID_INTEL_82371AB_0, ...); If the first lookup succeeds but the second fails, dev becomes NULL. This leads to a potential null-pointer dereference when dev_dbg() is called: if (errata.piix4.bmisx) dev_dbg(&dev->dev, ...); To prevent this, use two temporary pointers and retrieve each device independently, avoiding overwriting dev with a possible NULL value. Signed-off-by: Tuo Li --- v2: * Add checks for ide_dev and isa_dev before dev_dbg() Thanks Rafael J. Wysocki for helpful advice. --- drivers/acpi/acpi_processor.c | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c index 7ec1dc04fd11..e43978b0d83c 100644 --- a/drivers/acpi/acpi_processor.c +++ b/drivers/acpi/acpi_processor.c @@ -50,6 +50,7 @@ static int acpi_processor_errata_piix4(struct pci_dev *de= v) { u8 value1 =3D 0; u8 value2 =3D 0; + struct pci_dev *ide_dev, *isa_dev; =20 =20 if (!dev) @@ -107,12 +108,12 @@ static int acpi_processor_errata_piix4(struct pci_dev= *dev) * each IDE controller's DMA status to make sure we catch all * DMA activity. */ - dev =3D pci_get_subsys(PCI_VENDOR_ID_INTEL, + ide_dev =3D pci_get_subsys(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB, PCI_ANY_ID, PCI_ANY_ID, NULL); - if (dev) { - errata.piix4.bmisx =3D pci_resource_start(dev, 4); - pci_dev_put(dev); + if (ide_dev) { + errata.piix4.bmisx =3D pci_resource_start(ide_dev, 4); + pci_dev_put(ide_dev); } =20 /* @@ -124,24 +125,24 @@ static int acpi_processor_errata_piix4(struct pci_dev= *dev) * disable C3 support if this is enabled, as some legacy * devices won't operate well if fast DMA is disabled. */ - dev =3D pci_get_subsys(PCI_VENDOR_ID_INTEL, + isa_dev =3D pci_get_subsys(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_0, PCI_ANY_ID, PCI_ANY_ID, NULL); - if (dev) { - pci_read_config_byte(dev, 0x76, &value1); - pci_read_config_byte(dev, 0x77, &value2); + if (isa_dev) { + pci_read_config_byte(isa_dev, 0x76, &value1); + pci_read_config_byte(isa_dev, 0x77, &value2); if ((value1 & 0x80) || (value2 & 0x80)) errata.piix4.fdma =3D 1; - pci_dev_put(dev); + pci_dev_put(isa_dev); } =20 break; } =20 - if (errata.piix4.bmisx) - dev_dbg(&dev->dev, "Bus master activity detection (BM-IDE) erratum enabl= ed\n"); - if (errata.piix4.fdma) - dev_dbg(&dev->dev, "Type-F DMA livelock erratum (C3 disabled)\n"); + if (errata.piix4.bmisx && ide_dev) + dev_dbg(&ide_dev->dev, "Bus master activity detection (BM-IDE) erratum e= nabled\n"); + if (errata.piix4.fdma && isa_dev) + dev_dbg(&isa_dev->dev, "Type-F DMA livelock erratum (C3 disabled)\n"); =20 return 0; } --=20 2.43.0