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Date: Wed, 15 Jan 2020 17:23:19 -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 4/6] ubsan: Check panic_on_warn

Syzkaller expects kernel warnings to panic when the panic_on_warn
sysctl is set. More work is needed here to have UBSan reuse the WARN
infrastructure, but for now, just check the flag manually.

Link: https://lore.kernel.org/lkml/CACT4Y+bsLJ-wFx_TaXqax3JByUOWB3uk787LsyMVcfW6JzzGvg@mail.gmail.com
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 lib/ubsan.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/lib/ubsan.c b/lib/ubsan.c
index 7b9b58aee72c..429663eef6a7 100644
--- a/lib/ubsan.c
+++ b/lib/ubsan.c
@@ -156,6 +156,17 @@ static void ubsan_epilogue(void)
 		"========================================\n");
 
 	current->in_ubsan--;
+
+	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");
+	}
 }
 
 static void handle_overflow(struct overflow_data *data, void *lhs,
-- 
2.20.1

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