[PATCH v2 5/6] printk: insert newline in devkmsg_read()

[Alex Elder]

If a log record has LOG_PREFIX set, its predecessor record should be
terminated if it was marked LOG_CONT.  In devkmsg_read(), this
condition was being ignored, which would lead to such records
showing up combined when reading /dev/kmsg.  Fix this oversight.

Reported-by: Petr MlÃdek <pmladek@xxxxxxx>
Signed-off-by: Alex Elder <elder@xxxxxxxxxx>
---
 kernel/printk/printk.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index e5ee1cb..3174ba9 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -575,6 +575,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 	char cont;
 	size_t len;
 	ssize_t ret;
+	bool insert_newline;
 
 	if (!user)
 		return -EBADF;
@@ -626,7 +627,10 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 	else
 		cont = '-';
 
-	len = sprintf(user->buf, "%u,%llu,%llu,%c;",
+	/* Insert a newline if we're terminating the previous record early */
+	insert_newline = (user->prev & LOG_CONT) && (msg->flags & LOG_PREFIX);
+	len = sprintf(user->buf, "%s%u,%llu,%llu,%c;",
+		      insert_newline ? "\n" : "",
 		      (msg->facility << 3) | msg->level,
 		      user->seq, ts_usec, cont);
 	user->prev = msg->flags;
-- 
1.9.1

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