6.15-stable review patch. If anyone has any objections, please let me know.
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From: Niklas Schnelle schnelle@linux.ibm.com
commit 47c397844869ad0e6738afb5879c7492f4691122 upstream.
As disable_slot() takes a struct zpci_dev from the Configured to the Standby state. In Standby there is still a hotplug slot so this is not usually a case of sysfs self deletion. This is important because self deletion gets very hairy in terms of locking (see for example recover_store() in arch/s390/pci/pci_sysfs.c).
Because the pci_dev_put() is not within the critical section of the zdev->state_lock however, disable_slot() can turn into a case of self deletion if zPCI device event handling slips between the mutex_unlock() and the pci_dev_put(). If the latter is the last put and zpci_release_device() is called this then tries to remove the hotplug slot via zpci_exit_slot() which will try to remove the hotplug slot directory the disable_slot() is part of i.e. self deletion.
Prevent this by widening the zdev->state_lock critical section to include the pci_dev_put() which is then guaranteed to happen with the struct zpci_dev still in Standby state ensuring it will not lead to a zpci_release_device() call as at least the zPCI event handling code still holds a reference.
Cc: stable@vger.kernel.org Fixes: a46044a92add ("s390/pci: fix zpci_zdev_put() on reserve") Reviewed-by: Gerd Bayer gbayer@linux.ibm.com Tested-by: Gerd Bayer gbayer@linux.ibm.com Signed-off-by: Niklas Schnelle schnelle@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/pci/hotplug/s390_pci_hpc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/pci/hotplug/s390_pci_hpc.c +++ b/drivers/pci/hotplug/s390_pci_hpc.c @@ -65,9 +65,9 @@ static int disable_slot(struct hotplug_s
rc = zpci_deconfigure_device(zdev); out: - mutex_unlock(&zdev->state_lock); if (pdev) pci_dev_put(pdev); + mutex_unlock(&zdev->state_lock); return rc; }