[PATCH] kasan: make report_lock a raw spinlock

[Jared Kangas <jkangas@xxxxxxxxxx>]

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.

Link: https://lkml.kernel.org/r/20241119210234.1602529-1-jkangas@xxxxxxxxxx
Fixes: 342a93247e08 ("locking/spinlock: Provide RT variant header: <linux/spinlock_rt.h>")
Signed-off-by: Jared Kangas <jkangas@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 50fb19ad4388..3fe77a360f1c 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -201,7 +201,7 @@ 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)
 {
@@ -212,7 +212,7 @@ 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");
 }
 
@@ -222,7 +222,7 @@ 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) {