On Tue, Dec 22, 2015 at 01:44:51PM -0800, David Daney wrote:
> From: David Daney <david.daney@xxxxxxxxxx>
>
> The aer_inject module, when active, replaces the pci_ops structure of
> the bus so that it can intercept config space accesses. If the config
> space access needs to be forwarded to the original pci_ops, we must
> restore the bus's original ops, as the read()/write() functions may
> require use of the data in the pci_ops structure. An example of such
> functions are the pci_generic_config*() functions in
> drivers/pci/access.c. A failure to call these with a valid bus->ops
> results in dereferencing an invalid bus->ops->map_bus pointer and
> subsequent OOPs and system crash.
>
> So, do as suggested above. When calling to the original
> read()/write() functions, temporarily switch back to the original
> pci_ops. This is safe to do as the pci_lock must already be held, and
> thus no other users of the bus->ops are possible.
>
> Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
Applied to pci/aer for v4.6, thanks, David!
> ---
> drivers/pci/pcie/aer/aer_inject.c | 30 ++++++++++++++++++++++++++++--
> 1 file changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/pcie/aer/aer_inject.c b/drivers/pci/pcie/aer/aer_inject.c
> index 182224a..2d60e0e 100644
> --- a/drivers/pci/pcie/aer/aer_inject.c
> +++ b/drivers/pci/pcie/aer/aer_inject.c
> @@ -188,7 +188,9 @@ static int pci_read_aer(struct pci_bus *bus, unsigned int devfn, int where,
> struct aer_error *err;
> unsigned long flags;
> struct pci_ops *ops;
> + struct pci_ops *my_ops;
> int domain;
> + int rv;
>
> spin_lock_irqsave(&inject_lock, flags);
> if (size != sizeof(u32))
> @@ -208,8 +210,19 @@ static int pci_read_aer(struct pci_bus *bus, unsigned int devfn, int where,
> }
> out:
> ops = __find_pci_bus_ops(bus);
> + /*
> + * pci_lock must already be held, so we can directly
> + * manipulate bus->ops. Many config access functions,
> + * including pci_generic_config_read() require the original
> + * bus->ops be installed to function, so temporarily put them
> + * back.
> + */
> + my_ops = bus->ops;
> + bus->ops = ops;
> + rv = ops->read(bus, devfn, where, size, val);
> + bus->ops = my_ops;
> spin_unlock_irqrestore(&inject_lock, flags);
> - return ops->read(bus, devfn, where, size, val);
> + return rv;
> }
>
> static int pci_write_aer(struct pci_bus *bus, unsigned int devfn, int where,
> @@ -220,7 +233,9 @@ static int pci_write_aer(struct pci_bus *bus, unsigned int devfn, int where,
> unsigned long flags;
> int rw1cs;
> struct pci_ops *ops;
> + struct pci_ops *my_ops;
> int domain;
> + int rv;
>
> spin_lock_irqsave(&inject_lock, flags);
> if (size != sizeof(u32))
> @@ -243,8 +258,19 @@ static int pci_write_aer(struct pci_bus *bus, unsigned int devfn, int where,
> }
> out:
> ops = __find_pci_bus_ops(bus);
> + /*
> + * pci_lock must already be held, so we can directly
> + * manipulate bus->ops. Many config access functions,
> + * including pci_generic_config_write() require the original
> + * bus->ops be installed to function, so temporarily put them
> + * back.
> + */
> + my_ops = bus->ops;
> + bus->ops = ops;
> + rv = ops->write(bus, devfn, where, size, val);
> + bus->ops = my_ops;
> spin_unlock_irqrestore(&inject_lock, flags);
> - return ops->write(bus, devfn, where, size, val);
> + return rv;
> }
>
> static struct pci_ops pci_ops_aer = {
> --
> 1.8.3.1
>
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