| From: John Ogness <john.ogness@linutronix.de> |
| Date: Mon, 7 Oct 2019 16:20:39 +0200 |
| Subject: [PATCH] printk: handle iterating while buffer changing |
| |
| The syslog and kmsg_dump readers are provided buffers to fill. |
| Both try to maximize the provided buffer usage by calculating the |
| maximum number of messages that can fit. However, if after the |
| calculation, messages are dropped and new messages added, the |
| calculation will no longer match. |
| |
| For syslog, add a check to make sure the provided buffer is not |
| overfilled. |
| |
| For kmsg_dump, start over by recalculating the messages |
| available. |
| |
| Signed-off-by: John Ogness <john.ogness@linutronix.de> |
| Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> |
| --- |
| kernel/printk/printk.c | 5 ++++- |
| 1 file changed, 4 insertions(+), 1 deletion(-) |
| |
| --- a/kernel/printk/printk.c |
| +++ b/kernel/printk/printk.c |
| @@ -1446,6 +1446,9 @@ static int syslog_print_all(char __user |
| break; |
| } |
| |
| + if (len + textlen > size) |
| + break; |
| + |
| if (copy_to_user(buf + len, text, textlen)) |
| len = -EFAULT; |
| else |
| @@ -3086,7 +3089,7 @@ bool kmsg_dump_get_buffer(struct kmsg_du |
| ret = prb_iter_next(&iter, msgbuf, PRINTK_RECORD_MAX, &seq); |
| if (ret == 0) { |
| break; |
| - } else if (ret < 0) { |
| + } else if (ret < 0 || seq >= end_seq) { |
| prb_iter_init(&iter, &printk_rb, &seq); |
| goto retry; |
| } |
