From: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> kmsg_dump() allows to dump kmesg buffer for various system events: oops, panic, reboot, etc. It provides an interface to register a callback call for clients, and in that callback interface there is a field "max_reason" which gets ignored unless always_kmsg_dump is passed as kernel parameter. Allow clients to decide max_reason, and keep the current behavior when max_reason is not set. Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Link: https://lore.kernel.org/r/20200505154510.93506-2-pasha.tatashin@xxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- include/linux/kmsg_dump.h | 1 + kernel/printk/printk.c | 15 +++++++++++---- 2 files changed, 12 insertions(+), 4 deletions(-) diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h index 2e7a1e032c71..cfc042066be7 100644 --- a/include/linux/kmsg_dump.h +++ b/include/linux/kmsg_dump.h @@ -28,6 +28,7 @@ enum kmsg_dump_reason { KMSG_DUMP_RESTART, KMSG_DUMP_HALT, KMSG_DUMP_POWEROFF, + KMSG_DUMP_MAX }; /** diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 9a9b6156270b..1aab69a8a2bf 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3157,12 +3157,19 @@ void kmsg_dump(enum kmsg_dump_reason reason) struct kmsg_dumper *dumper; unsigned long flags; - if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump) - return; - rcu_read_lock(); list_for_each_entry_rcu(dumper, &dump_list, list) { - if (dumper->max_reason && reason > dumper->max_reason) + enum kmsg_dump_reason cur_reason = dumper->max_reason; + + /* + * If client has not provided a specific max_reason, default + * to KMSG_DUMP_OOPS, unless always_kmsg_dump was set. + */ + if (cur_reason == KMSG_DUMP_UNDEF) { + cur_reason = always_kmsg_dump ? KMSG_DUMP_MAX : + KMSG_DUMP_OOPS; + } + if (reason > cur_reason) continue; /* initialize iterator with data about the stored records */ -- 2.20.1
