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| author | Niklas Schnelle <schnelle@linux.ibm.com> | 2021-08-06 12:11:16 +0200 |
|---|---|---|
| committer | Sasha Levin <sashal@kernel.org> | 2021-08-26 08:35:56 -0400 |
| commit | a69326e134d4ffa0d2d77bf1a4a62271c51c3051 (patch) | |
| tree | d0278a7242f892471aa98d4c476176ba63ba46ea /arch/s390 | |
| parent | 05b56e05543c41ae738aea25918c140735cc9870 (diff) | |
s390/pci: fix use after free of zpci_dev
[ 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>
Diffstat (limited to 'arch/s390')
| -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 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, |