From: John Ogness Date: Wed, 16 Nov 2022 16:21:19 +0000 (+0106) Subject: um: kmsg_dump: only dump when no output console available X-Git-Tag: v6.2-rc1~213^2^2~34 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3860e7c57fd23e744e045436f9872fb9d01381e2;p=thirdparty%2Fkernel%2Flinux.git um: kmsg_dump: only dump when no output console available The initial intention of the UML kmsg_dumper is to dump the kernel buffers to stdout if there is no console available to perform the regular crash output. However, if ttynull was registered as a console, no crash output was seen. Commit e23fe90dec28 ("um: kmsg_dumper: always dump when not tty console") tried to fix this by performing the kmsg_dump unless the stdio console was behind /dev/console or enabled. But this allowed kmsg dumping to occur even if other non-stdio consoles will output the crash output. Also, a console being the driver behind /dev/console has nothing to do with a crash scenario. Restore the initial intention by dumping the kernel buffers to stdout only if a non-ttynull console is registered and enabled. Also add detailed comments so that it is clear why these rules are applied. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20221116162152.193147-8-john.ogness@linutronix.de --- diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c index 0224fcb36e22c..40abf1e9ccb16 100644 --- a/arch/um/kernel/kmsg_dump.c +++ b/arch/um/kernel/kmsg_dump.c @@ -17,13 +17,22 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, unsigned long flags; size_t len = 0; - /* only dump kmsg when no console is available */ + /* + * If no consoles are available to output crash information, dump + * the kmsg buffer to stdout. + */ + if (!console_trylock()) return; for_each_console(con) { - if(strcmp(con->name, "tty") == 0 && - (con->flags & (CON_ENABLED | CON_CONSDEV)) != 0) { + /* + * The ttynull console and disabled consoles are ignored + * since they cannot output. All other consoles are + * expected to output the crash information. + */ + if (strcmp(con->name, "ttynull") != 0 && + (con->flags & CON_ENABLED)) { break; } }