From: John Ogness john.ogness@linutronix.de
[ Upstream commit 668af87f995b6d6d09595c088ad1fb5dd9ff25d2 ]
Counting text lines in a record simply involves counting the number of newline characters (+1). However, it is searching the full data block for newline characters, even though the text data can be (and often is) a subset of that area. Since the extra area in the data block was never initialized, the result is that extra newlines may be seen and counted.
Restrict newline searching to the text data length.
Fixes: b6cf8b3f3312 ("printk: add lockless ringbuffer") Signed-off-by: John Ogness john.ogness@linutronix.de Reviewed-by: Petr Mladek pmladek@suse.com Acked-by: Sergey Senozhatsky sergey.senozhatsky@gmail.com Signed-off-by: Petr Mladek pmladek@suse.com Link: https://lore.kernel.org/r/20210113144234.6545-1-john.ogness@linutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/printk/printk_ringbuffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 74e25a1704f2b..617dd63589650 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -1720,7 +1720,7 @@ static bool copy_data(struct prb_data_ring *data_ring,
/* Caller interested in the line count? */ if (line_count) - *line_count = count_lines(data, data_size); + *line_count = count_lines(data, len);
/* Caller interested in the data content? */ if (!buf || !buf_size)