5.10-stable review patch. If anyone has any objections, please let me know.
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From: John Ogness john.ogness@linutronix.de
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 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 Cc: Brian Norris briannorris@chromium.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/debug/kdb/kdb_io.c | 2 ++ 1 file changed, 2 insertions(+)
--- 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 *ms 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