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.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Elena Petrova <lenaptr@google.com>
Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Link: https://lore.kernel.org/lkml/CACT4Y+bsLJ-wFx_TaXqax3JByUOWB3uk787LsyMVcfW6JzzGvg@mail.gmail.com
Link: http://lkml.kernel.org/r/20200227193516.32566-5-keescook@chromium.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/ubsan.c b/lib/ubsan.c
index 7b9b58a..429663e 100644 (file)
--- 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,