linux-kernel - [PATCH] kasan: make report

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Message-ID: <20241119210234.1602529-1-jkangas@redhat.com>
Date: Tue, 19 Nov 2024 13:02:34 -0800
From: Jared Kangas <jkangas@...hat.com>
To: ryabinin.a.a@...il.com
Cc: glider@...gle.com,
	andreyknvl@...il.com,
	dvyukov@...gle.com,
	vincenzo.frascino@....com,
	akpm@...ux-foundation.org,
	kasan-dev@...glegroups.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Jared Kangas <jkangas@...hat.com>
Subject: [PATCH] kasan: make report_lock a raw spinlock

If PREEMPT_RT is enabled, report_lock is a sleeping spinlock and must
not be locked when IRQs are disabled. However, KASAN reports may be
triggered in such contexts. For example:

        char *s = kzalloc(1, GFP_KERNEL);
        kfree(s);
        local_irq_disable();
        char c = *s;  /* KASAN report here leads to spin_lock() */
        local_irq_enable();

Make report_spinlock a raw spinlock to prevent rescheduling when
PREEMPT_RT is enabled.

Signed-off-by: Jared Kangas <jkangas@...hat.com>
---
 mm/kasan/report.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index b48c768acc84..c7c0083203cb 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -200,7 +200,7 @@ static inline void fail_non_kasan_kunit_test(void) { }
 
 #endif /* CONFIG_KUNIT */
 
-static DEFINE_SPINLOCK(report_lock);
+static DEFINE_RAW_SPINLOCK(report_lock);
 
 static void start_report(unsigned long *flags, bool sync)
 {
@@ -211,7 +211,7 @@ static void start_report(unsigned long *flags, bool sync)
 	lockdep_off();
 	/* Make sure we don't end up in loop. */
 	report_suppress_start();
-	spin_lock_irqsave(&report_lock, *flags);
+	raw_spin_lock_irqsave(&report_lock, *flags);
 	pr_err("==================================================================\n");
 }
 
@@ -221,7 +221,7 @@ static void end_report(unsigned long *flags, const void *addr, bool is_write)
 		trace_error_report_end(ERROR_DETECTOR_KASAN,
 				       (unsigned long)addr);
 	pr_err("==================================================================\n");
-	spin_unlock_irqrestore(&report_lock, *flags);
+	raw_spin_unlock_irqrestore(&report_lock, *flags);
 	if (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 		check_panic_on_warn("KASAN");
 	switch (kasan_arg_fault) {
-- 
2.47.0