[PATCH v12 6/6] mm: kasan: Do not panic if both panic_on_warn and kasan_multishot set

[David Gow <davidgow@google.com>]

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>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Tested-by: Andrey Konovalov <andreyknvl@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 e2c14b10bc81..00a53f1355ae 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -95,7 +95,7 @@ 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 && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
 		/*
 		 * This thread may hit another WARN() in the panic path.
 		 * Resetting this prevents additional WARN() from panicking the
-- 
2.28.0.236.gb10cc79966-goog