From: Niklas Schnelle schnelle@linux.ibm.com
[ Upstream commit 2a671f77ee49f3e78997b77fdee139467ff6a598 ]
The struct pci_dev uses reference counting but zPCI assumed erroneously that the last reference would always be the local reference after calling pci_stop_and_remove_bus_device(). This is usually the case but not how reference counting works and thus inherently fragile.
In fact one case where this causes a NULL pointer dereference when on an SRIOV device the function 0 was hot unplugged before another function of the same multi-function device. In this case the second function's pdev->sriov->dev reference keeps the struct pci_dev of function 0 alive even after the unplug. This bug was previously hidden by the fact that we were leaking the struct pci_dev which in turn means that it always outlived the struct zpci_dev. This was fixed in commit 0b13525c20fe ("s390/pci: fix leak of PCI device structure") exposing the broken behavior.
Fix this by accounting for the long living reference a struct pci_dev has to its underlying struct zpci_dev via the zbus->function[] array and only release that in pcibios_release_device() ensuring that the struct pci_dev is not left with a dangling reference. This is a minimal fix in the future it would probably better to use fine grained reference counting for struct zpci_dev.
Fixes: 05bc1be6db4b2 ("s390/pci: create zPCI bus") Cc: stable@vger.kernel.org Reviewed-by: Matthew Rosato mjrosato@linux.ibm.com Signed-off-by: Niklas Schnelle schnelle@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/pci/pci.c | 6 ++++++ arch/s390/pci/pci_bus.h | 5 +++++ 2 files changed, 11 insertions(+)
diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c index 1ae7a76ae97b..ca1a105e3b5d 100644 --- a/arch/s390/pci/pci.c +++ b/arch/s390/pci/pci.c @@ -558,9 +558,12 @@ static void zpci_cleanup_bus_resources(struct zpci_dev *zdev)
int pcibios_add_device(struct pci_dev *pdev) { + struct zpci_dev *zdev = to_zpci(pdev); struct resource *res; int i;
+ /* The pdev has a reference to the zdev via its bus */ + zpci_zdev_get(zdev); if (pdev->is_physfn) pdev->no_vf_scan = 1;
@@ -580,7 +583,10 @@ int pcibios_add_device(struct pci_dev *pdev)
void pcibios_release_device(struct pci_dev *pdev) { + struct zpci_dev *zdev = to_zpci(pdev); + zpci_unmap_resources(pdev); + zpci_zdev_put(zdev); }
int pcibios_enable_device(struct pci_dev *pdev, int mask) diff --git a/arch/s390/pci/pci_bus.h b/arch/s390/pci/pci_bus.h index f8dfac0b5b71..55c9488e504c 100644 --- a/arch/s390/pci/pci_bus.h +++ b/arch/s390/pci/pci_bus.h @@ -16,6 +16,11 @@ static inline void zpci_zdev_put(struct zpci_dev *zdev) kref_put(&zdev->kref, zpci_release_device); }
+static inline void zpci_zdev_get(struct zpci_dev *zdev) +{ + kref_get(&zdev->kref); +} + int zpci_alloc_domain(int domain); void zpci_free_domain(int domain); int zpci_setup_bus_resources(struct zpci_dev *zdev,