linux-kernel - [PATCH 5.9 004/105] kprobes: Tell lockdep about kprobe nesting

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

Message-Id: <20201214172555.494155808@linuxfoundation.org>
Date:   Mon, 14 Dec 2020 18:27:38 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 5.9 004/105] kprobes: Tell lockdep about kprobe nesting

From: Steven Rostedt (VMware) <rostedt@...dmis.org>

commit 645f224e7ba2f4200bf163153d384ceb0de5462e upstream.

Since the kprobe handlers have protection that prohibits other handlers from
executing in other contexts (like if an NMI comes in while processing a
kprobe, and executes the same kprobe, it will get fail with a "busy"
return). Lockdep is unaware of this protection. Use lockdep's nesting api to
differentiate between locks taken in INT3 context and other context to
suppress the false warnings.

Link: https://lore.kernel.org/r/20201102160234.fa0ae70915ad9e2b21c08b85@kernel.org

Cc: stable@...r.kernel.org # 5.9.x
Cc: Peter Zijlstra <peterz@...radead.org>
Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/kprobes.c |   25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1250,7 +1250,13 @@ __acquires(hlist_lock)
 
 	*head = &kretprobe_inst_table[hash];
 	hlist_lock = kretprobe_table_lock_ptr(hash);
-	raw_spin_lock_irqsave(hlist_lock, *flags);
+	/*
+	 * Nested is a workaround that will soon not be needed.
+	 * There's other protections that make sure the same lock
+	 * is not taken on the same CPU that lockdep is unaware of.
+	 * Differentiate when it is taken in NMI context.
+	 */
+	raw_spin_lock_irqsave_nested(hlist_lock, *flags, !!in_nmi());
 }
 NOKPROBE_SYMBOL(kretprobe_hash_lock);
 
@@ -1259,7 +1265,13 @@ static void kretprobe_table_lock(unsigne
 __acquires(hlist_lock)
 {
 	raw_spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash);
-	raw_spin_lock_irqsave(hlist_lock, *flags);
+	/*
+	 * Nested is a workaround that will soon not be needed.
+	 * There's other protections that make sure the same lock
+	 * is not taken on the same CPU that lockdep is unaware of.
+	 * Differentiate when it is taken in NMI context.
+	 */
+	raw_spin_lock_irqsave_nested(hlist_lock, *flags, !!in_nmi());
 }
 NOKPROBE_SYMBOL(kretprobe_table_lock);
 
@@ -1942,7 +1954,12 @@ static int pre_handler_kretprobe(struct
 
 	/* TODO: consider to only swap the RA after the last pre_handler fired */
 	hash = hash_ptr(current, KPROBE_HASH_BITS);
-	raw_spin_lock_irqsave(&rp->lock, flags);
+	/*
+	 * Nested is a workaround that will soon not be needed.
+	 * There's other protections that make sure the same lock
+	 * is not taken on the same CPU that lockdep is unaware of.
+	 */
+	raw_spin_lock_irqsave_nested(&rp->lock, flags, 1);
 	if (!hlist_empty(&rp->free_instances)) {
 		ri = hlist_entry(rp->free_instances.first,
 				struct kretprobe_instance, hlist);
@@ -1953,7 +1970,7 @@ static int pre_handler_kretprobe(struct
 		ri->task = current;
 
 		if (rp->entry_handler && rp->entry_handler(ri, regs)) {
-			raw_spin_lock_irqsave(&rp->lock, flags);
+			raw_spin_lock_irqsave_nested(&rp->lock, flags, 1);
 			hlist_add_head(&ri->hlist, &rp->free_instances);
 			raw_spin_unlock_irqrestore(&rp->lock, flags);
 			return 0;