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  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]
Date:   Tue, 15 Jan 2019 16:55:44 -0500
From:   Waiman Long <>
To:     Peter Zijlstra <>,
        Ingo Molnar <>,
        Will Deacon <>
        Zhenzhong Duan <>,
        James Morse <>,
        Borislav Petkov <>,
        SRINIVAS <>,
        Waiman Long <>
Subject: [PATCH] locking/qspinlock: Add bug check for exceeding MAX_NODES

On some architectures, it is possible to have nested NMIs taking
spinlocks nestedly. Even though the chance of having more than 4 nested
spinlocks with contention is extremely small, there could still be a
possibility that it may happen some days leading to system panic.

What we don't want is a silent corruption with system panic somewhere
else. So add a BUG_ON() check to make sure that a system panic caused
by this will show the correct root cause.

Signed-off-by: Waiman Long <>
 kernel/locking/qspinlock.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 8a8c3c2..f823221 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -412,6 +412,16 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
 	idx = node->count++;
 	tail = encode_tail(smp_processor_id(), idx);
+	/*
+	 * 4 nodes are allocated based on the assumption that there will
+	 * not be nested NMIs taking spinlocks. That may not be true in
+	 * some architectures even though the chance of needing more than
+	 * 4 nodes will still be extremely unlikely. Adding a bug check
+	 * here to make sure there won't be a silent corruption in case
+	 * this condition happens.
+	 */
+	BUG_ON(idx >= MAX_NODES);
 	node = grab_mcs_node(node, idx);

Powered by blists - more mailing lists