kmsg_dump_rewind_nolock() accesses @clear_seq without any locking. However, accessing this global variable requires holding @logbuf_lock. For the _nolock() variant, start from the first record in the ringbuffer rather than the @clear_seq record.
Signed-off-by: John Ogness <[email protected]> --- kernel/printk/printk.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 00bc1fce3299..cff13b33e926 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3410,11 +3410,12 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer); * kmsg_dump_get_buffer() can be called again and used multiple * times within the same dumper.dump() callback. * - * The function is similar to kmsg_dump_rewind(), but grabs no locks. + * The function is similar to kmsg_dump_rewind(), but grabs no locks + * and starts from the oldest record rather than from @clear_seq. */ void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper) { - dumper->cur_seq = clear_seq; + dumper->cur_seq = 0; dumper->next_seq = prb_next_seq(prb); } @@ -3431,7 +3432,8 @@ void kmsg_dump_rewind(struct kmsg_dumper *dumper) unsigned long flags; logbuf_lock_irqsave(flags); - kmsg_dump_rewind_nolock(dumper); + dumper->cur_seq = clear_seq; + dumper->next_seq = prb_next_seq(prb); logbuf_unlock_irqrestore(flags); } EXPORT_SYMBOL_GPL(kmsg_dump_rewind); -- 2.20.1
