From: Niklas Schnelle Date: Thu, 22 May 2025 12:13:13 +0000 (+0200) Subject: s390/pci: Prevent self deletion in disable_slot() X-Git-Tag: v6.16-rc1~201^2~2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=47c397844869ad0e6738afb5879c7492f4691122;p=thirdparty%2Flinux.git s390/pci: Prevent self deletion in disable_slot() 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 Tested-by: Gerd Bayer Signed-off-by: Niklas Schnelle Signed-off-by: Heiko Carstens --- diff --git a/drivers/pci/hotplug/s390_pci_hpc.c b/drivers/pci/hotplug/s390_pci_hpc.c index 055518ee354dc..3d26d273f29d1 100644 --- a/drivers/pci/hotplug/s390_pci_hpc.c +++ b/drivers/pci/hotplug/s390_pci_hpc.c @@ -66,9 +66,9 @@ static int disable_slot(struct hotplug_slot *hotplug_slot) rc = zpci_deconfigure_device(zdev); out: - mutex_unlock(&zdev->state_lock); if (pdev) pci_dev_put(pdev); + mutex_unlock(&zdev->state_lock); return rc; }