From 392d2826c5d7f4578619346a10a1f293ceea7827 Mon Sep 17 00:00:00 2001 From: John Ogness Date: Mon, 17 Jul 2023 21:52:01 +0206 Subject: [PATCH] kdb: Do not assume write() callback available commit 6d3e0d8cc63221dec670d0ee92ac57961581e975 upstream. 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 Reviewed-by: Petr Mladek Reviewed-by: Douglas Anderson Reviewed-by: Daniel Thompson Acked-by: Daniel Thompson Reviewed-by: Sergey Senozhatsky Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20230717194607.145135-2-john.ogness@linutronix.de Cc: Brian Norris Signed-off-by: Greg Kroah-Hartman --- 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 b28b8a5ef6381..1d016767179f5 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -577,6 +577,8 @@ 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 -- 2.47.3