path: root/arch
diff options
authorNiklas Schnelle <>2021-08-06 12:11:16 +0200
committerVasily Gorbik <>2021-08-18 10:12:42 +0200
commit2a671f77ee49f3e78997b77fdee139467ff6a598 (patch)
tree8c470515944ea145aa11ef5facb9fcb248bc3fe4 /arch
parent7c60610d476766e128cc4284bb6349732cbd6606 (diff)
s390/pci: fix use after free of zpci_dev
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: Reviewed-by: Matthew Rosato <> Signed-off-by: Niklas Schnelle <> Signed-off-by: Vasily Gorbik <>
Diffstat (limited to 'arch')
2 files changed, 11 insertions, 0 deletions
diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
index b0993e05affe..8fcb7ecb7225 100644
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -560,9 +560,12 @@ 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;
@@ -582,7 +585,10 @@ int pcibios_add_device(struct pci_dev *pdev)
void pcibios_release_device(struct pci_dev *pdev)
+ struct zpci_dev *zdev = to_zpci(pdev);
+ zpci_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 b877a97e6745..e359d2686178 100644
--- a/arch/s390/pci/pci_bus.h
+++ b/arch/s390/pci/pci_bus.h
@@ -22,6 +22,11 @@ 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,