This is a note to let you know that I've just added the patch titled powerpc/MSI: Fix race condition in tearing down MSI interrupts to the 4.2-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: powerpc-msi-fix-race-condition-in-tearing-down-msi-interrupts.patch and it can be found in the queue-4.2 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From e297c939b745e420ef0b9dc989cb87bda617b399 Mon Sep 17 00:00:00 2001 From: Paul Mackerras <paulus@xxxxxxxxxx> Date: Thu, 10 Sep 2015 14:36:21 +1000 Subject: powerpc/MSI: Fix race condition in tearing down MSI interrupts From: Paul Mackerras <paulus@xxxxxxxxxx> commit e297c939b745e420ef0b9dc989cb87bda617b399 upstream. This fixes a race which can result in the same virtual IRQ number being assigned to two different MSI interrupts. The most visible consequence of that is usually a warning and stack trace from the sysfs code about an attempt to create a duplicate entry in sysfs. The race happens when one CPU (say CPU 0) is disposing of an MSI while another CPU (say CPU 1) is setting up an MSI. CPU 0 calls (for example) pnv_teardown_msi_irqs(), which calls msi_bitmap_free_hwirqs() to indicate that the MSI (i.e. its hardware IRQ number) is no longer in use. Then, before CPU 0 gets to calling irq_dispose_mapping() to free up the virtal IRQ number, CPU 1 comes in and calls msi_bitmap_alloc_hwirqs() to allocate an MSI, and gets the same hardware IRQ number that CPU 0 just freed. CPU 1 then calls irq_create_mapping() to get a virtual IRQ number, which sees that there is currently a mapping for that hardware IRQ number and returns the corresponding virtual IRQ number (which is the same virtual IRQ number that CPU 0 was using). CPU 0 then calls irq_dispose_mapping() and frees that virtual IRQ number. Now, if another CPU comes along and calls irq_create_mapping(), it is likely to get the virtual IRQ number that was just freed, resulting in the same virtual IRQ number apparently being used for two different hardware interrupts. To fix this race, we just move the call to msi_bitmap_free_hwirqs() to after the call to irq_dispose_mapping(). Since virq_to_hw() doesn't work for the virtual IRQ number after irq_dispose_mapping() has been called, we need to call it before irq_dispose_mapping() and remember the result for the msi_bitmap_free_hwirqs() call. The pattern of calling msi_bitmap_free_hwirqs() before irq_dispose_mapping() appears in 5 places under arch/powerpc, and appears to have originated in commit 05af7bd2d75e ("[POWERPC] MPIC U3/U4 MSI backend") from 2007. Fixes: 05af7bd2d75e ("[POWERPC] MPIC U3/U4 MSI backend") Reported-by: Alexey Kardashevskiy <aik@xxxxxxxxx> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/powerpc/platforms/pasemi/msi.c | 5 +++-- arch/powerpc/platforms/powernv/pci.c | 5 +++-- arch/powerpc/sysdev/fsl_msi.c | 5 +++-- arch/powerpc/sysdev/mpic_u3msi.c | 5 +++-- arch/powerpc/sysdev/ppc4xx_msi.c | 5 +++-- 5 files changed, 15 insertions(+), 10 deletions(-) --- a/arch/powerpc/platforms/pasemi/msi.c +++ b/arch/powerpc/platforms/pasemi/msi.c @@ -63,6 +63,7 @@ static struct irq_chip mpic_pasemi_msi_c static void pasemi_msi_teardown_msi_irqs(struct pci_dev *pdev) { struct msi_desc *entry; + irq_hw_number_t hwirq; pr_debug("pasemi_msi_teardown_msi_irqs, pdev %p\n", pdev); @@ -70,10 +71,10 @@ static void pasemi_msi_teardown_msi_irqs if (entry->irq == NO_IRQ) continue; + hwirq = virq_to_hw(entry->irq); irq_set_msi_desc(entry->irq, NULL); - msi_bitmap_free_hwirqs(&msi_mpic->msi_bitmap, - virq_to_hw(entry->irq), ALLOC_CHUNK); irq_dispose_mapping(entry->irq); + msi_bitmap_free_hwirqs(&msi_mpic->msi_bitmap, hwirq, ALLOC_CHUNK); } return; --- a/arch/powerpc/platforms/powernv/pci.c +++ b/arch/powerpc/platforms/powernv/pci.c @@ -99,6 +99,7 @@ void pnv_teardown_msi_irqs(struct pci_de struct pci_controller *hose = pci_bus_to_host(pdev->bus); struct pnv_phb *phb = hose->private_data; struct msi_desc *entry; + irq_hw_number_t hwirq; if (WARN_ON(!phb)) return; @@ -106,10 +107,10 @@ void pnv_teardown_msi_irqs(struct pci_de list_for_each_entry(entry, &pdev->msi_list, list) { if (entry->irq == NO_IRQ) continue; + hwirq = virq_to_hw(entry->irq); irq_set_msi_desc(entry->irq, NULL); - msi_bitmap_free_hwirqs(&phb->msi_bmp, - virq_to_hw(entry->irq) - phb->msi_base, 1); irq_dispose_mapping(entry->irq); + msi_bitmap_free_hwirqs(&phb->msi_bmp, hwirq - phb->msi_base, 1); } } #endif /* CONFIG_PCI_MSI */ --- a/arch/powerpc/sysdev/fsl_msi.c +++ b/arch/powerpc/sysdev/fsl_msi.c @@ -128,15 +128,16 @@ static void fsl_teardown_msi_irqs(struct { struct msi_desc *entry; struct fsl_msi *msi_data; + irq_hw_number_t hwirq; list_for_each_entry(entry, &pdev->msi_list, list) { if (entry->irq == NO_IRQ) continue; + hwirq = virq_to_hw(entry->irq); msi_data = irq_get_chip_data(entry->irq); irq_set_msi_desc(entry->irq, NULL); - msi_bitmap_free_hwirqs(&msi_data->bitmap, - virq_to_hw(entry->irq), 1); irq_dispose_mapping(entry->irq); + msi_bitmap_free_hwirqs(&msi_data->bitmap, hwirq, 1); } return; --- a/arch/powerpc/sysdev/mpic_u3msi.c +++ b/arch/powerpc/sysdev/mpic_u3msi.c @@ -107,15 +107,16 @@ static u64 find_u4_magic_addr(struct pci static void u3msi_teardown_msi_irqs(struct pci_dev *pdev) { struct msi_desc *entry; + irq_hw_number_t hwirq; list_for_each_entry(entry, &pdev->msi_list, list) { if (entry->irq == NO_IRQ) continue; + hwirq = virq_to_hw(entry->irq); irq_set_msi_desc(entry->irq, NULL); - msi_bitmap_free_hwirqs(&msi_mpic->msi_bitmap, - virq_to_hw(entry->irq), 1); irq_dispose_mapping(entry->irq); + msi_bitmap_free_hwirqs(&msi_mpic->msi_bitmap, hwirq, 1); } return; --- a/arch/powerpc/sysdev/ppc4xx_msi.c +++ b/arch/powerpc/sysdev/ppc4xx_msi.c @@ -124,16 +124,17 @@ void ppc4xx_teardown_msi_irqs(struct pci { struct msi_desc *entry; struct ppc4xx_msi *msi_data = &ppc4xx_msi; + irq_hw_number_t hwirq; dev_dbg(&dev->dev, "PCIE-MSI: tearing down msi irqs\n"); list_for_each_entry(entry, &dev->msi_list, list) { if (entry->irq == NO_IRQ) continue; + hwirq = virq_to_hw(entry->irq); irq_set_msi_desc(entry->irq, NULL); - msi_bitmap_free_hwirqs(&msi_data->bitmap, - virq_to_hw(entry->irq), 1); irq_dispose_mapping(entry->irq); + msi_bitmap_free_hwirqs(&msi_data->bitmap, hwirq, 1); } } Patches currently in stable-queue which might be from paulus@xxxxxxxxxx are queue-4.2/powerpc-msi-fix-race-condition-in-tearing-down-msi-interrupts.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html