+ kasan-make-report_lock-a-raw-spinlock.patch added to mm-hotfixes-unstable branch

+ kasan-make-report_lock-a-raw-spinlock.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: kasan: make report_lock a raw spinlock
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     kasan-make-report_lock-a-raw-spinlock.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kasan-make-report_lock-a-raw-spinlock.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Jared Kangas <jkangas@redhat.com>
Subject: kasan: make report_lock a raw spinlock
Date: Tue, 19 Nov 2024 13:02:34 -0800

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@redhat.com
Signed-off-by: Jared Kangas <jkangas@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/kasan/report.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/kasan/report.c~kasan-make-report_lock-a-raw-spinlock
+++ a/mm/kasan/report.c
@@ -200,7 +200,7 @@ static inline void fail_non_kasan_kunit_
 
 #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 *
 	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 *fl
 		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) {
_

Patches currently in -mm which might be from jkangas@redhat.com are

kasan-make-report_lock-a-raw-spinlock.patch