linux-kernel - [PATCH MANUALSEL 4.19 1/4] x86/nmi: Make register_nmi

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220605135519.61765-1-sashal@kernel.org>
Date:   Sun,  5 Jun 2022 09:55:11 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <seanjc@...gle.com>,
        Borislav Petkov <bp@...e.de>, Sasha Levin <sashal@...nel.org>,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, peterz@...radead.org, jkosina@...e.cz
Subject: [PATCH MANUALSEL 4.19 1/4] x86/nmi: Make register_nmi_handler() more robust

From: Thomas Gleixner <tglx@...utronix.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@...gle.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lore.kernel.org/lkml/20220511234332.3654455-1-seanjc@google.com
Signed-off-by: Sasha Levin <sashal@...nel.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 996eb53f8eb7..75b68e499315 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -158,7 +158,7 @@ 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);
@@ -178,7 +178,7 @@ 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;
 }
@@ -187,7 +187,7 @@ 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);
@@ -201,12 +201,16 @@ 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);
 
-- 
2.35.1