linux-hardening - [PATCH 5.10 03/20] panic: unset panic_on

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Message-Id: <20230124193004.206841-4-ebiggers@kernel.org>
Date:   Tue, 24 Jan 2023 11:29:47 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     stable@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Kees Cook <keescook@...omium.org>, SeongJae Park <sj@...nel.org>,
        Seth Jenkins <sethjenkins@...gle.com>,
        Jann Horn <jannh@...gle.com>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Baoquan He <bhe@...hat.com>, Jonathan Corbet <corbet@....net>,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Marco Elver <elver@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.10 03/20] panic: unset panic_on_warn inside panic()

From: Tiezhu Yang <yangtiezhu@...ngson.cn>

commit 1a2383e8b84c0451fd9b1eec3b9aab16f30b597c upstream.

In the current code, the following three places need to unset
panic_on_warn before calling panic() to avoid recursive panics:

kernel/kcsan/report.c: print_report()
kernel/sched/core.c: __schedule_bug()
mm/kfence/report.c: kfence_report_error()

In order to avoid copy-pasting "panic_on_warn = 0" all over the places,
it is better to move it inside panic() and then remove it from the other
places.

Link: https://lkml.kernel.org/r/1644324666-15947-4-git-send-email-yangtiezhu@loongson.cn
Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
Reviewed-by: Marco Elver <elver@...gle.com>
Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc: Baoquan He <bhe@...hat.com>
Cc: Jonathan Corbet <corbet@....net>
Cc: Xuefeng Li <lixuefeng@...ngson.cn>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 kernel/panic.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/kernel/panic.c b/kernel/panic.c
index f567195d45d9d..960c2be2759cb 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -207,6 +207,16 @@ void panic(const char *fmt, ...)
 	int old_cpu, this_cpu;
 	bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
 
+	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;
+	}
+
 	/*
 	 * Disable local interrupts. This will prevent panic_smp_self_stop
 	 * from deadlocking the first cpu that invokes the panic, since
@@ -618,16 +628,8 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 	if (regs)
 		show_regs(regs);
 
-	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;
+	if (panic_on_warn)
 		panic("panic_on_warn set ...\n");
-	}
 
 	if (!regs)
 		dump_stack();
-- 
2.39.1