diff options
Diffstat (limited to '0001-xen-events-avoid-removing-an-event-channel-while-han.patch')
| -rw-r--r-- | 0001-xen-events-avoid-removing-an-event-channel-while-han.patch | 161 |
1 files changed, 0 insertions, 161 deletions
diff --git a/0001-xen-events-avoid-removing-an-event-channel-while-han.patch b/0001-xen-events-avoid-removing-an-event-channel-while-han.patch deleted file mode 100644 index cd4ac3df3..000000000 --- a/0001-xen-events-avoid-removing-an-event-channel-while-han.patch +++ /dev/null @@ -1,161 +0,0 @@ -From 073d0552ead5bfc7a3a9c01de590e924f11b5dd2 Mon Sep 17 00:00:00 2001 -From: Juergen Gross <jgross@suse.com> -Date: Mon, 7 Sep 2020 15:47:27 +0200 -Subject: [PATCH] xen/events: avoid removing an event channel while handling it -MIME-Version: 1.0 -Content-Type: text/plain; charset=UTF-8 -Content-Transfer-Encoding: 8bit - -Today it can happen that an event channel is being removed from the -system while the event handling loop is active. This can lead to a -race resulting in crashes or WARN() splats when trying to access the -irq_info structure related to the event channel. - -Fix this problem by using a rwlock taken as reader in the event -handling loop and as writer when deallocating the irq_info structure. - -As the observed problem was a NULL dereference in evtchn_from_irq() -make this function more robust against races by testing the irq_info -pointer to be not NULL before dereferencing it. - -And finally make all accesses to evtchn_to_irq[row][col] atomic ones -in order to avoid seeing partial updates of an array element in irq -handling. Note that irq handling can be entered only for event channels -which have been valid before, so any not populated row isn't a problem -in this regard, as rows are only ever added and never removed. - -This is XSA-331. - -Cc: stable@vger.kernel.org -Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> -Reported-by: Jinoh Kang <luke1337@theori.io> -Signed-off-by: Juergen Gross <jgross@suse.com> -Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> -Reviewed-by: Wei Liu <wl@xen.org> ---- - drivers/xen/events/events_base.c | 41 ++++++++++++++++++++++++++++---- - 1 file changed, 36 insertions(+), 5 deletions(-) - -diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c -index 6f02c18fa65c..407741ece084 100644 ---- a/drivers/xen/events/events_base.c -+++ b/drivers/xen/events/events_base.c -@@ -33,6 +33,7 @@ - #include <linux/slab.h> - #include <linux/irqnr.h> - #include <linux/pci.h> -+#include <linux/spinlock.h> - - #ifdef CONFIG_X86 - #include <asm/desc.h> -@@ -71,6 +72,23 @@ const struct evtchn_ops *evtchn_ops; - */ - static DEFINE_MUTEX(irq_mapping_update_lock); - -+/* -+ * Lock protecting event handling loop against removing event channels. -+ * Adding of event channels is no issue as the associated IRQ becomes active -+ * only after everything is setup (before request_[threaded_]irq() the handler -+ * can't be entered for an event, as the event channel will be unmasked only -+ * then). -+ */ -+static DEFINE_RWLOCK(evtchn_rwlock); -+ -+/* -+ * Lock hierarchy: -+ * -+ * irq_mapping_update_lock -+ * evtchn_rwlock -+ * IRQ-desc lock -+ */ -+ - static LIST_HEAD(xen_irq_list_head); - - /* IRQ <-> VIRQ mapping. */ -@@ -105,7 +123,7 @@ static void clear_evtchn_to_irq_row(unsigned row) - unsigned col; - - for (col = 0; col < EVTCHN_PER_ROW; col++) -- evtchn_to_irq[row][col] = -1; -+ WRITE_ONCE(evtchn_to_irq[row][col], -1); - } - - static void clear_evtchn_to_irq_all(void) -@@ -142,7 +160,7 @@ static int set_evtchn_to_irq(evtchn_port_t evtchn, unsigned int irq) - clear_evtchn_to_irq_row(row); - } - -- evtchn_to_irq[row][col] = irq; -+ WRITE_ONCE(evtchn_to_irq[row][col], irq); - return 0; - } - -@@ -152,7 +170,7 @@ int get_evtchn_to_irq(evtchn_port_t evtchn) - return -1; - if (evtchn_to_irq[EVTCHN_ROW(evtchn)] == NULL) - return -1; -- return evtchn_to_irq[EVTCHN_ROW(evtchn)][EVTCHN_COL(evtchn)]; -+ return READ_ONCE(evtchn_to_irq[EVTCHN_ROW(evtchn)][EVTCHN_COL(evtchn)]); - } - - /* Get info for IRQ */ -@@ -261,10 +279,14 @@ static void xen_irq_info_cleanup(struct irq_info *info) - */ - evtchn_port_t evtchn_from_irq(unsigned irq) - { -- if (WARN(irq >= nr_irqs, "Invalid irq %d!\n", irq)) -+ const struct irq_info *info = NULL; -+ -+ if (likely(irq < nr_irqs)) -+ info = info_for_irq(irq); -+ if (!info) - return 0; - -- return info_for_irq(irq)->evtchn; -+ return info->evtchn; - } - - unsigned int irq_from_evtchn(evtchn_port_t evtchn) -@@ -440,16 +462,21 @@ static int __must_check xen_allocate_irq_gsi(unsigned gsi) - static void xen_free_irq(unsigned irq) - { - struct irq_info *info = info_for_irq(irq); -+ unsigned long flags; - - if (WARN_ON(!info)) - return; - -+ write_lock_irqsave(&evtchn_rwlock, flags); -+ - list_del(&info->list); - - set_info_for_irq(irq, NULL); - - WARN_ON(info->refcnt > 0); - -+ write_unlock_irqrestore(&evtchn_rwlock, flags); -+ - kfree(info); - - /* Legacy IRQ descriptors are managed by the arch. */ -@@ -1233,6 +1260,8 @@ static void __xen_evtchn_do_upcall(void) - struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu); - int cpu = smp_processor_id(); - -+ read_lock(&evtchn_rwlock); -+ - do { - vcpu_info->evtchn_upcall_pending = 0; - -@@ -1243,6 +1272,8 @@ static void __xen_evtchn_do_upcall(void) - virt_rmb(); /* Hypervisor can set upcall pending. */ - - } while (vcpu_info->evtchn_upcall_pending); -+ -+ read_unlock(&evtchn_rwlock); - } - - void xen_evtchn_do_upcall(struct pt_regs *regs) --- -2.28.0 - |