logger: handle logs of odd length correctly

If there was only one byte left before the buffer wraps around,
the length field, which consists of 2 bytes, would end up torn apart,
yielding garbage on naive read attempts.

While libdlog did ensure to write only even-length logs, this could
not be relied upon when not using it: this includes kmsg and, potentially,
malicious users.

Change-Id: I7ec3777d650ec2642812b27e87de5e16e0dd72fc
Signed-off-by: Michal Bloch <m.bloch@samsung.com>

diff --git a/src/logger/logger.c b/src/logger/logger.c
index 39afcd5..87663ec 100644 (file)
--- a/src/logger/logger.c
+++ b/src/logger/logger.c
@@ -899,8 +899,10 @@ static int print_out_logs(struct logger *server, struct reader *reader)
        }
 
        while (from != buffer->tail && (!reader->dumpcount || (reader->bytes_to_read > 0))) {
-               ple = (struct logger_entry*)(buffer->buffer + from);
-               copy_from_buffer(tmp, from, ple->len, buffer);
+               typeof(ple->len) length;
+               copy_from_buffer(&length, from, sizeof length, buffer);
+
+               copy_from_buffer(tmp, from, length, buffer);
                ple = (struct logger_entry*)tmp;
 
                from += ple->len;