From f03a0118769a0e3334b7a5f994a6a32a3d9dc307 Mon Sep 17 00:00:00 2001 From: John Ogness Date: Thu, 28 Jan 2021 20:45:43 +0800 Subject: [PATCH] printk: ringbuffer: fix line counting stable inclusion from stable-5.10.11 commit cf3cca5f1580ce846e36c32db2c125199dca2d86 bugzilla: 47621 -------------------------------- [ 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 Reviewed-by: Petr Mladek Acked-by: Sergey Senozhatsky Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20210113144234.6545-1-john.ogness@linutronix.de Signed-off-by: Sasha Levin Signed-off-by: Zheng Zengkai Acked-by: Xie XiuQi --- 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 74e25a1704f2..617dd6358965 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) -- GitLab