console: fix out-of-bounds read in dputc(/dev/*, ...)

Trying to output a single character via
	echo -a /dev/serial0-1
currently results in garbage output after the newline, because console.c's
fops_write discards the buffer length and passes the buffer to
(struct cdev)::puts which only handles NUL-terminated strings.

Fix this by amending (struct cdev)::puts with a new nbytes parameter,
which is correctly propagated. All this functions now return at most the
nbytes parameter they were passed in. This fixes __console_puts, which
used to count new lines twice in its return value.

Fixes: b4f55fcf35 ("console: expose consoles in devfs")
Cc: Bastian Krause <bst@pengutronix.de>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 29 insertions, 0 deletions

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 0a6fa38edc..15c0174b1f 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -46,6 +46,35 @@ void pstore_set_kmsg_bytes(int bytes)
 
 static int pstore_ready;
 
+static void pstore_console_write(const char *s, unsigned c)
+{
+	const char *e = s + c;
+
+	while (s < e) {
+		struct pstore_record record = {
+			.type = PSTORE_TYPE_CONSOLE,
+			.psi = psinfo,
+		};
+
+		if (c > psinfo->bufsize)
+			c = psinfo->bufsize;
+
+		record.buf = (char *)s;
+		record.size = c;
+		psinfo->write_buf(PSTORE_TYPE_CONSOLE, 0, &record.id, 0,
+				  record.buf, 0, record.size, psinfo);
+		s += c;
+		c = e - s;
+	}
+}
+
+static int pstore_console_puts(struct console_device *cdev, const char *s,
+			       size_t nbytes)
+{
+	pstore_console_write(s, nbytes);
+	return nbytes;
+}
+
 void pstore_log(const char *str)
 {
 	uint64_t id;