From:   Eric Biggers <ebiggers@kernel.org>
To:     stable@vger.kernel.org
Cc:     Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>,
        Kees Cook <keescook@chromium.org>,
        SeongJae Park <sj@kernel.org>,
        Seth Jenkins <sethjenkins@google.com>,
        Jann Horn <jannh@google.com>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Patricia Alfonso <trishalfonso@google.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Shuah Khan <shuah@kernel.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        David Gow <davidgow@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrey Konovalov <andreyknvl@google.com>,
        Brendan Higgins <brendanhiggins@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 4.19 03/16] mm: kasan: do not panic if both panic_on_warn and kasan_multishot set
Date:   Wed,  1 Feb 2023 21:25:51 -0800
Message-Id: <20230202052604.179184-4-ebiggers@kernel.org>
In-Reply-To: <20230202052604.179184-1-ebiggers@kernel.org>
References: <20230202052604.179184-1-ebiggers@kernel.org>
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From: David Gow <davidgow@google.com>

commit be4f1ae978ffe98cc95ec49ceb95386fb4474974 upstream.

KASAN errors will currently trigger a panic when panic_on_warn is set.
This renders kasan_multishot useless, as further KASAN errors won't be
reported if the kernel has already paniced.  By making kasan_multishot
disable this behaviour for KASAN errors, we can still have the benefits of
panic_on_warn for non-KASAN warnings, yet be able to use kasan_multishot.

This is particularly important when running KASAN tests, which need to
trigger multiple KASAN errors: previously these would panic the system if
panic_on_warn was set, now they can run (and will panic the system should
non-KASAN warnings show up).

Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Patricia Alfonso <trishalfonso@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20200915035828.570483-6-davidgow@google.com
Link: https://lkml.kernel.org/r/20200910070331.3358048-6-davidgow@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 mm/kasan/report.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 5c169aa688fde..90fdb261a5e2d 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -176,7 +176,7 @@ static void kasan_end_report(unsigned long *flags)
 	pr_err("==================================================================\n");
 	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 	spin_unlock_irqrestore(&report_lock, *flags);
-	if (panic_on_warn)
+	if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 		panic("panic_on_warn set ...\n");
 	kasan_enable_current();
 }
-- 
2.39.1