From 6d3e0d8cc63221dec670d0ee92ac57961581e975 Mon Sep 17 00:00:00 2001 From: John Ogness <john.ogness@linutronix.de> Date: Mon, 17 Jul 2023 21:52:01 +0206 Subject: [PATCH] kdb: Do not assume write() callback available It is allowed for consoles to not provide a write() callback. For example ttynull does this. Check if a write() callback is available before using it. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Reviewed-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org> Acked-by: Daniel Thompson <daniel.thompson@linaro.org> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230717194607.145135-2-john.ogness@linutronix.de --- kernel/debug/kdb/kdb_io.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 5c7e9ba7cd6b2..e9139dfc1f0a8 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -576,6 +576,8 @@ static void kdb_msg_write(const char *msg, int msg_len) continue; if (c == dbg_io_ops->cons) continue; + if (!c->write) + continue; /* * Set oops_in_progress to encourage the console drivers to * disregard their internal spin locks: in the current calling -- GitLab