linux-kernel - [PATCH 5/5] kfence: unset panic_on

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Date:   Fri, 28 Jan 2022 19:42:25 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Baoquan He <bhe@...hat.com>, Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Marco Elver <elver@...gle.com>
Cc:     kexec@...ts.infradead.org, linux-doc@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 5/5] kfence: 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: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 mm/kfence/report.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/mm/kfence/report.c b/mm/kfence/report.c
index f93a7b2..9d61a23 100644
--- a/mm/kfence/report.c
+++ b/mm/kfence/report.c
@@ -267,8 +267,16 @@ void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *r
 
 	lockdep_on();
 
-	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");
+	}
 
 	/* We encountered a memory safety error, taint the kernel! */
 	add_taint(TAINT_BAD_PAGE, LOCKDEP_STILL_OK);
-- 
2.1.0