1 files changed, 38 insertions, 17 deletions

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index d6e9d08..cf56614 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -810,33 +810,54 @@ static const struct file_operations oldmem_fops = {
 static ssize_t kmsg_writev(struct kiocb *iocb, const struct iovec *iv,
 			   unsigned long count, loff_t pos)
 {
-	char *line, *p;
+	char *buf, *line;
 	int i;
-	ssize_t ret = -EFAULT;
+	int level = default_message_loglevel;
+	int facility = 1;	/* LOG_USER */
 	size_t len = iov_length(iv, count);
+	ssize_t ret = len;
 
-	line = kmalloc(len + 1, GFP_KERNEL);
-	if (line == NULL)
+	if (len > 1024)
+		return -EINVAL;
+	buf = kmalloc(len+1, GFP_KERNEL);
+	if (buf == NULL)
 		return -ENOMEM;
 
-	/*
-	 * copy all vectors into a single string, to ensure we do
-	 * not interleave our log line with other printk calls
-	 */
-	p = line;
+	line = buf;
 	for (i = 0; i < count; i++) {
-		if (copy_from_user(p, iv[i].iov_base, iv[i].iov_len))
+		if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len))
 			goto out;
-		p += iv[i].iov_len;
+		line += iv[i].iov_len;
+	}
+
+	/*
+	 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
+	 * the decimal value represents 32bit, the lower 3 bit are the log
+	 * level, the rest are the log facility.
+	 *
+	 * If no prefix or no userspace facility is specified, we
+	 * enforce LOG_USER, to be able to reliably distinguish
+	 * kernel-generated messages from userspace-injected ones.
+	 */
+	line = buf;
+	if (line[0] == '<') {
+		char *endp = NULL;
+
+		i = simple_strtoul(line+1, &endp, 10);
+		if (endp && endp[0] == '>') {
+			level = i & 7;
+			if (i >> 3)
+				facility = i >> 3;
+			endp++;
+			len -= endp - line;
+			line = endp;
+		}
 	}
-	p[0] = '\0';
+	line[len] = '\0';
 
-	ret = printk("%s", line);
-	/* printk can add a prefix */
-	if (ret > len)
-		ret = len;
+	printk_emit(facility, level, NULL, 0, "%s", line);
 out:
-	kfree(line);
+	kfree(buf);
 	return ret;
 }