From 4e32c4c7016eeb2186ffa4ebcbadbddc4b071234 Mon Sep 17 00:00:00 2001 From: Niklas Schnelle Date: Mon, 20 Sep 2021 09:32:21 +0200 Subject: [PATCH] s390/pci: improve zpci_dev reference counting [ Upstream commit c122383d221dfa2f41cfe5e672540595de986fde ] Currently zpci_dev uses kref based reference counting but only accounts for one original reference plus one reference from an added pci_dev to its underlying zpci_dev. Counting just the original reference worked until the pci_dev reference was added in commit 2a671f77ee49 ("s390/pci: fix use after free of zpci_dev") because once a zpci_dev goes away, i.e. enters the reserved state, it would immediately get released. However with the pci_dev reference this is no longer the case and the zpci_dev may still appear in multiple availability events indicating that it was reserved. This was solved by detecting when the zpci_dev is already on its way out but still hanging around. This has however shown some light on how unusual our zpci_dev reference counting is. Improve upon this by modelling zpci_dev reference counting on pci_dev. Analogous to pci_get_slot() increment the reference count in get_zdev_by_fid(). Thus all users of get_zdev_by_fid() must drop the reference once they are done with the zpci_dev. Similar to pci_scan_single_device(), zpci_create_device() returns the device with an initial count of 1 and the device added to the zpci_list (analogous to the PCI bus' device_list). In turn users of zpci_create_device() must only drop the reference once the device is gone from the point of view of the zPCI subsystem, it might still be referenced by the common PCI subsystem though. Reviewed-by: Matthew Rosato Signed-off-by: Niklas Schnelle Signed-off-by: Vasily Gorbik Signed-off-by: Sasha Levin --- arch/s390/pci/pci.c | 1 + arch/s390/pci/pci_bus.h | 3 ++- arch/s390/pci/pci_clp.c | 9 +++++++-- arch/s390/pci/pci_event.c | 7 ++++++- 4 files changed, 16 insertions(+), 4 deletions(-) diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c index b833155..639924d 100644 --- a/arch/s390/pci/pci.c +++ b/arch/s390/pci/pci.c @@ -69,6 +69,7 @@ struct zpci_dev *get_zdev_by_fid(u32 fid) list_for_each_entry(tmp, &zpci_list, entry) { if (tmp->fid == fid) { zdev = tmp; + zpci_zdev_get(zdev); break; } } diff --git a/arch/s390/pci/pci_bus.h b/arch/s390/pci/pci_bus.h index e359d26..ecef3a9 100644 --- a/arch/s390/pci/pci_bus.h +++ b/arch/s390/pci/pci_bus.h @@ -19,7 +19,8 @@ void zpci_bus_remove_device(struct zpci_dev *zdev, bool set_error); void zpci_release_device(struct kref *kref); static inline void zpci_zdev_put(struct zpci_dev *zdev) { - kref_put(&zdev->kref, zpci_release_device); + if (zdev) + kref_put(&zdev->kref, zpci_release_device); } static inline void zpci_zdev_get(struct zpci_dev *zdev) diff --git a/arch/s390/pci/pci_clp.c b/arch/s390/pci/pci_clp.c index be077b3..5011d27 100644 --- a/arch/s390/pci/pci_clp.c +++ b/arch/s390/pci/pci_clp.c @@ -22,6 +22,8 @@ #include #include +#include "pci_bus.h" + bool zpci_unique_uid; void update_uid_checking(bool new) @@ -403,8 +405,11 @@ static void __clp_add(struct clp_fh_list_entry *entry, void *data) return; zdev = get_zdev_by_fid(entry->fid); - if (!zdev) - zpci_create_device(entry->fid, entry->fh, entry->config_state); + if (zdev) { + zpci_zdev_put(zdev); + return; + } + zpci_create_device(entry->fid, entry->fh, entry->config_state); } int clp_scan_pci_devices(void) diff --git a/arch/s390/pci/pci_event.c b/arch/s390/pci/pci_event.c index 5b8d647..6d57625 100644 --- a/arch/s390/pci/pci_event.c +++ b/arch/s390/pci/pci_event.c @@ -62,10 +62,12 @@ static void __zpci_event_error(struct zpci_ccdf_err *ccdf) pdev ? pci_name(pdev) : "n/a", ccdf->pec, ccdf->fid); if (!pdev) - return; + goto no_pdev; pdev->error_state = pci_channel_io_perm_failure; pci_dev_put(pdev); +no_pdev: + zpci_zdev_put(zdev); } void zpci_event_error(void *data) @@ -94,6 +96,7 @@ static void zpci_event_hard_deconfigured(struct zpci_dev *zdev, u32 fh) static void __zpci_event_availability(struct zpci_ccdf_avail *ccdf) { struct zpci_dev *zdev = get_zdev_by_fid(ccdf->fid); + bool existing_zdev = !!zdev; enum zpci_state state; zpci_err("avail CCDF:\n"); @@ -156,6 +159,8 @@ static void __zpci_event_availability(struct zpci_ccdf_avail *ccdf) default: break; } + if (existing_zdev) + zpci_zdev_put(zdev); } void zpci_event_availability(void *data) -- 2.7.4