The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 47c397844869ad0e6738afb5879c7492f4691122 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025062052-deviate-fetal-1fef@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 47c397844869ad0e6738afb5879c7492f4691122 Mon Sep 17 00:00:00 2001 From: Niklas Schnelle schnelle@linux.ibm.com Date: Thu, 22 May 2025 14:13:13 +0200 Subject: [PATCH] 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 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
diff --git a/drivers/pci/hotplug/s390_pci_hpc.c b/drivers/pci/hotplug/s390_pci_hpc.c index 055518ee354d..3d26d273f29d 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; }