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| author | Niklas Schnelle <schnelle@linux.ibm.com> | 2021-08-06 12:11:16 +0200 |
|---|---|---|
| committer | Vasily Gorbik <gor@linux.ibm.com> | 2021-08-18 10:12:42 +0200 |
| commit | 2a671f77ee49f3e78997b77fdee139467ff6a598 (patch) | |
| tree | 8c470515944ea145aa11ef5facb9fcb248bc3fe4 /arch | |
| parent | 7c60610d476766e128cc4284bb6349732cbd6606 (diff) | |
| download | linux-2a671f77ee49f3e78997b77fdee139467ff6a598.tar.gz | |
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: 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>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/s390/pci/pci.c | 6 | ||||
| -rw-r--r-- | arch/s390/pci/pci_bus.h | 5 |
2 files changed, 11 insertions, 0 deletions
diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c index b0993e05affe65..8fcb7ecb7225ad 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_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 b877a97e6745bc..e359d2686178b8 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, |