linux-kernel - [PATCH v4 4/6] ubsan: Check panic_on

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Message-Id: <20200227184921.30215-5-keescook@chromium.org>
Date:   Thu, 27 Feb 2020 10:49:19 -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>,
        Andrey Konovalov <andreyknvl@...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 v4 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