[PATCH 4.19 02/16] panic: unset panic_on_warn inside panic()

[Eric Biggers]

From: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>

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@xxxxxxxxxxx
Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Xuefeng Li <lixuefeng@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
 kernel/panic.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/kernel/panic.c b/kernel/panic.c
index 8138a676fb7d1..a078d413042f2 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -142,6 +142,16 @@ 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
@@ -530,16 +540,8 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 	if (args)
 		vprintk(args->fmt, args->args);
 
-	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");
-	}
 
 	print_modules();
 
-- 
2.39.1