From: Thomas Gleixner tglx@linutronix.de
[ Upstream commit a7fed5c0431dbfa707037848830f980e0f93cfb3 ]
register_nmi_handler() has no sanity check whether a handler has been registered already. Such an unintended double-add leads to list corruption and hard to diagnose problems during the next NMI handling.
Init the list head in the static NMI action struct and check it for being empty in register_nmi_handler().
[ bp: Fixups. ]
Reported-by: Sean Christopherson seanjc@google.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Borislav Petkov bp@suse.de Link: https://lore.kernel.org/lkml/20220511234332.3654455-1-seanjc@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/include/asm/nmi.h | 1 + arch/x86/kernel/nmi.c | 12 ++++++++---- 2 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/nmi.h b/arch/x86/include/asm/nmi.h index 9d5d949e662e..655ca59acfe7 100644 --- a/arch/x86/include/asm/nmi.h +++ b/arch/x86/include/asm/nmi.h @@ -48,6 +48,7 @@ struct nmiaction { #define register_nmi_handler(t, fn, fg, n, init...) \ ({ \ static struct nmiaction init fn##_na = { \ + .list = LIST_HEAD_INIT(fn##_na.list), \ .handler = (fn), \ .name = (n), \ .flags = (fg), \ diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c index 2ef961cf4cfc..11e98d6d25e7 100644 --- a/arch/x86/kernel/nmi.c +++ b/arch/x86/kernel/nmi.c @@ -157,7 +157,7 @@ int __register_nmi_handler(unsigned int type, struct nmiaction *action) struct nmi_desc *desc = nmi_to_desc(type); unsigned long flags;
- if (!action->handler) + if (WARN_ON_ONCE(!action->handler || !list_empty(&action->list))) return -EINVAL;
raw_spin_lock_irqsave(&desc->lock, flags); @@ -177,7 +177,7 @@ int __register_nmi_handler(unsigned int type, struct nmiaction *action) list_add_rcu(&action->list, &desc->head); else list_add_tail_rcu(&action->list, &desc->head); - + raw_spin_unlock_irqrestore(&desc->lock, flags); return 0; } @@ -186,7 +186,7 @@ EXPORT_SYMBOL(__register_nmi_handler); void unregister_nmi_handler(unsigned int type, const char *name) { struct nmi_desc *desc = nmi_to_desc(type); - struct nmiaction *n; + struct nmiaction *n, *found = NULL; unsigned long flags;
raw_spin_lock_irqsave(&desc->lock, flags); @@ -200,12 +200,16 @@ void unregister_nmi_handler(unsigned int type, const char *name) WARN(in_nmi(), "Trying to free NMI (%s) from NMI context!\n", n->name); list_del_rcu(&n->list); + found = n; break; } }
raw_spin_unlock_irqrestore(&desc->lock, flags); - synchronize_rcu(); + if (found) { + synchronize_rcu(); + INIT_LIST_HEAD(&found->list); + } } EXPORT_SYMBOL_GPL(unregister_nmi_handler);