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 774a1fa880bc949d88b5ddec9494a13be733dfa8 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025062020-oxygen-print-635f@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 774a1fa880bc949d88b5ddec9494a13be733dfa8 Mon Sep 17 00:00:00 2001 From: Niklas Schnelle schnelle@linux.ibm.com Date: Thu, 22 May 2025 14:13:15 +0200 Subject: [PATCH] s390/pci: Serialize device addition and removal

Prior changes ensured that when zpci_release_device() is called and it removed the zdev from the zpci_list this instance can not be found via the zpci_list anymore even while allowing re-add of reserved devices. This only accounts for the overall lifetime and zpci_list addition and removal, it does not yet prevent concurrent add of a new instance for the same underlying device. Such concurrent add would subsequently cause issues such as attempted re-use of the same IOMMU sysfs directory and is generally undesired.

Introduce a new zpci_add_remove_lock mutex to serialize adding a new device with removal. Together this ensures that if a struct zpci_dev is not found in the zpci_list it was either already removed and torn down, or its removal and tear down is in progress with the zpci_add_remove_lock held.

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/arch/s390/pci/pci.c b/arch/s390/pci/pci.c index 4602abd0c6f1..cd6676c2d602 100644 --- a/arch/s390/pci/pci.c +++ b/arch/s390/pci/pci.c @@ -45,6 +45,7 @@ /* list of all detected zpci devices */ static LIST_HEAD(zpci_list); static DEFINE_SPINLOCK(zpci_list_lock); +static DEFINE_MUTEX(zpci_add_remove_lock);

static DECLARE_BITMAP(zpci_domain, ZPCI_DOMAIN_BITMAP_SIZE); static DEFINE_SPINLOCK(zpci_domain_lock); @@ -74,7 +75,9 @@ void zpci_zdev_put(struct zpci_dev *zdev) { if (!zdev) return; + mutex_lock(&zpci_add_remove_lock); kref_put_lock(&zdev->kref, zpci_release_device, &zpci_list_lock); + mutex_unlock(&zpci_add_remove_lock); }

struct zpci_dev *get_zdev_by_fid(u32 fid) @@ -844,6 +847,7 @@ int zpci_add_device(struct zpci_dev *zdev) { int rc;

+ mutex_lock(&zpci_add_remove_lock); zpci_dbg(1, "add fid:%x, fh:%x, c:%d\n", zdev->fid, zdev->fh, zdev->state); rc = zpci_init_iommu(zdev); if (rc) @@ -857,12 +861,14 @@ int zpci_add_device(struct zpci_dev *zdev) spin_lock(&zpci_list_lock); list_add_tail(&zdev->entry, &zpci_list); spin_unlock(&zpci_list_lock); + mutex_unlock(&zpci_add_remove_lock); return 0;

error_destroy_iommu: zpci_destroy_iommu(zdev); error: zpci_dbg(0, "add fid:%x, rc:%d\n", zdev->fid, rc); + mutex_unlock(&zpci_add_remove_lock); return rc; }

@@ -953,6 +959,7 @@ void zpci_release_device(struct kref *kref) { struct zpci_dev *zdev = container_of(kref, struct zpci_dev, kref);

+ lockdep_assert_held(&zpci_add_remove_lock); WARN_ON(zdev->state != ZPCI_FN_STATE_RESERVED); /* * We already hold zpci_list_lock thanks to kref_put_lock().