1 files changed, 44 insertions, 0 deletions
diff --git a/debian/patches-rt/printk-handle-iterating-while-buffer-changing.patch b/debian/patches-rt/printk-handle-iterating-while-buffer-changing.patch
new file mode 100644
index 000000000..6b64b9ca9
--- /dev/null
+++ b/debian/patches-rt/printk-handle-iterating-while-buffer-changing.patch
@@ -0,0 +1,44 @@
+From: John Ogness <john.ogness@linutronix.de>
+Date: Mon, 7 Oct 2019 16:20:39 +0200
+Subject: [PATCH] printk: handle iterating while buffer changing
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patches-5.4.3-rt1.tar.xz
+
+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
+@@ -3085,7 +3088,7 @@ 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;
+ 		}