From 396996cb7c00ab0b4f82ea9316ae4bd833546605 Mon Sep 17 00:00:00 2001 From: Tyrel Datwyler Date: Mon, 17 Apr 2017 20:21:40 -0400 Subject: [PATCH] powerpc/pseries: Fix of_node_put() underflow during DLPAR remove Historically struct device_node references were tracked using a kref embedded as a struct field. Commit f092332aeeee ("of: Make device nodes kobjects so they show up in sysfs") (Mar 2014) refactored device_nodes to be kobjects such that the device tree could by more simply exposed to userspace using sysfs. Commit 7f94fe081420 ("of: device_node kobject lifecycle fixes") (Mar 2014) followed up these changes to better control the kobject lifecycle and in particular the referecne counting via of_node_get(), of_node_put(), and of_node_init(). A result of this second commit was that it introduced an of_node_put() call when a dynamic node is detached, in of_node_remove(), that removes the initial kobj reference created by of_node_init(). Traditionally as the original dynamic device node user the pseries code had assumed responsibilty for releasing this final reference in its platform specific DLPAR detach code. This patch fixes a refcount underflow introduced by commit 7f94fe0814, and recently exposed by the upstreaming of the recount API. Messages like the following are no longer seen in the kernel log with this patch following DLPAR remove operations of cpus and pci devices. rpadlpar_io: slot PHB 72 removed refcount_t: underflow; use-after-free. ------------[ cut here ]------------ WARNING: CPU: 5 PID: 3335 at lib/refcount.c:128 refcount_sub_and_test+0xf4/0x110 Fixes: 7f94fe081420 ("of: device_node kobject lifecycle fixes") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Tyrel Datwyler [mpe: Make change log commit references more verbose] Signed-off-by: Michael Ellerman --- arch/powerpc/platforms/pseries/dlpar.c | 1 - 1 file changed, 1 deletion(-) diff --git a/arch/powerpc/platforms/pseries/dlpar.c b/arch/powerpc/platforms/pseries/dlpar.c index 193e052fa0dd8..bda18d8e1674b 100644 --- a/arch/powerpc/platforms/pseries/dlpar.c +++ b/arch/powerpc/platforms/pseries/dlpar.c @@ -288,7 +288,6 @@ int dlpar_detach_node(struct device_node *dn) if (rc) return rc; - of_node_put(dn); /* Must decrement the refcount */ return 0; } -- 2.39.5