powerpc/MSI: Fix race condition in tearing down MSI interrupts

[ Upstream commit e297c939b745e420ef0b9dc989cb87bda617b399 ]

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")
Cc: stable@vger.kernel.org # v2.6.22+
Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
index 4b20f2c6b3b24ba950d3ea10014e0b1fffbfc0b6..9ff55d59ac7695e5772103d7099f734e63a9c230 100644 (file)
--- a/arch/powerpc/platforms/powernv/pci.c
+++ b/arch/powerpc/platforms/powernv/pci.c
@@ -100,6 +100,7 @@ static void pnv_teardown_msi_irqs(struct pci_dev *pdev)
        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;
@@ -107,10 +108,10 @@ static void pnv_teardown_msi_irqs(struct pci_dev *pdev)
        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 */

diff --git a/arch/powerpc/sysdev/fsl_msi.c b/arch/powerpc/sysdev/fsl_msi.c
index da08ed08815751cec116164e8f6d3e828bda9fd4..ea6b3a1c79d87593b92909e20d5d205b6afa8915 100644 (file)
--- a/arch/powerpc/sysdev/fsl_msi.c
+++ b/arch/powerpc/sysdev/fsl_msi.c
@@ -129,15 +129,16 @@ static void fsl_teardown_msi_irqs(struct pci_dev *pdev)
 {
        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;

diff --git a/arch/powerpc/sysdev/mpic_pasemi_msi.c b/arch/powerpc/sysdev/mpic_pasemi_msi.c
index 15dccd35fa11a9d1fae5f1ca3fad180983693165..a6add4ae6c5a468ef1e0e523d966db4c62b345f5 100644 (file)
--- a/arch/powerpc/sysdev/mpic_pasemi_msi.c
+++ b/arch/powerpc/sysdev/mpic_pasemi_msi.c
@@ -66,6 +66,7 @@ static struct irq_chip mpic_pasemi_msi_chip = {
 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);
 
@@ -73,10 +74,11 @@ static void pasemi_msi_teardown_msi_irqs(struct pci_dev *pdev)
                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;

diff --git a/arch/powerpc/sysdev/mpic_u3msi.c b/arch/powerpc/sysdev/mpic_u3msi.c
index 623d7fba15b4d3c22d9bba0299bc516a9d85a6be..db35a4073127db69b55cbda676349ed80bc5b07f 100644 (file)
--- a/arch/powerpc/sysdev/mpic_u3msi.c
+++ b/arch/powerpc/sysdev/mpic_u3msi.c
@@ -108,15 +108,16 @@ static u64 find_u4_magic_addr(struct pci_dev *pdev, unsigned int hwirq)
 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;

diff --git a/arch/powerpc/sysdev/ppc4xx_msi.c b/arch/powerpc/sysdev/ppc4xx_msi.c
index 22b5200636e7f90299702d64d6b63ea1a5fe228f..85d9c1852d19e37db6ad5e4c8947b8aaebef47cd 100644 (file)
--- a/arch/powerpc/sysdev/ppc4xx_msi.c
+++ b/arch/powerpc/sysdev/ppc4xx_msi.c
@@ -125,16 +125,17 @@ void ppc4xx_teardown_msi_irqs(struct pci_dev *dev)
 {
        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);
        }
 }