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Date: Wed, 15 Jan 2020 17:23:20 -0800
From: Kees Cook <keescook@...omium.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Kees Cook <keescook@...omium.org>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Elena Petrova <lenaptr@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	"Gustavo A. R. Silva" <gustavo@...eddedor.com>,
	Arnd Bergmann <arnd@...db.de>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	kasan-dev@...glegroups.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	kernel-hardening@...ts.openwall.com,
	syzkaller@...glegroups.com
Subject: [PATCH v3 5/6] kasan: Unset panic_on_warn before calling panic()

As done in the full WARN() handler, panic_on_warn needs to be cleared
before calling panic() to avoid recursive panics.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 mm/kasan/report.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 621782100eaa..844554e78893 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -92,8 +92,16 @@ static void 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) {
+		/*
+		 * This thread may hit another WARN() in the panic path.
+		 * Resetting this prevents additional WARN() from panicking the
+		 * system on this thread.  Other threads are blocked by the
+		 * panic_mutex in panic().
+		 */
+		panic_on_warn = 0;
 		panic("panic_on_warn set ...\n");
+	}
 	kasan_enable_current();
 }
 
-- 
2.20.1

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