tracing: Use trace_seq_used() and seq_buf_used() instead of len
As the seq_buf->len will soon be +1 size when there's an overflow, we
must use trace_seq_used() or seq_buf_used() methods to get the real
length. This will prevent buffer overflow issues if just the len
of the seq_buf descriptor is used to copy memory.
Link: http://lkml.kernel.org/r/20141114121911.09ba3d38@gandalf.local.home
Reported-by: Petr Mladek <pmladek@suse.cz>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h
index 85d3710..cfaf5a1 100644
--- a/include/linux/trace_seq.h
+++ b/include/linux/trace_seq.h
@@ -24,6 +24,24 @@
}
/**
+ * trace_seq_used - amount of actual data written to buffer
+ * @s: trace sequence descriptor
+ *
+ * Returns the amount of data written to the buffer.
+ *
+ * IMPORTANT!
+ *
+ * Use this instead of @s->seq.len if you need to pass the amount
+ * of data from the buffer to another buffer (userspace, or what not).
+ * The @s->seq.len on overflow is bigger than the buffer size and
+ * using it can cause access to undefined memory.
+ */
+static inline int trace_seq_used(struct trace_seq *s)
+{
+ return seq_buf_used(&s->seq);
+}
+
+/**
* trace_seq_buffer_ptr - return pointer to next location in buffer
* @s: trace sequence descriptor
*
@@ -35,7 +53,7 @@
static inline unsigned char *
trace_seq_buffer_ptr(struct trace_seq *s)
{
- return s->buffer + s->seq.len;
+ return s->buffer + seq_buf_used(&s->seq);
}
/**
diff --git a/kernel/trace/seq_buf.c b/kernel/trace/seq_buf.c
index 9ec5305..ce17f65 100644
--- a/kernel/trace/seq_buf.c
+++ b/kernel/trace/seq_buf.c
@@ -328,7 +328,7 @@
if (s->len <= s->readpos)
return -EBUSY;
- len = s->len - s->readpos;
+ len = seq_buf_used(s) - s->readpos;
if (cnt > len)
cnt = len;
ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 0aa75be..9023446 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -944,10 +944,10 @@
{
int len;
- if (s->seq.len <= s->seq.readpos)
+ if (trace_seq_used(s) <= s->seq.readpos)
return -EBUSY;
- len = s->seq.len - s->seq.readpos;
+ len = trace_seq_used(s) - s->seq.readpos;
if (cnt > len)
cnt = len;
memcpy(buf, s->buffer + s->seq.readpos, cnt);
@@ -4514,18 +4514,18 @@
trace_access_lock(iter->cpu_file);
while (trace_find_next_entry_inc(iter) != NULL) {
enum print_line_t ret;
- int len = iter->seq.seq.len;
+ int save_len = iter->seq.seq.len;
ret = print_trace_line(iter);
if (ret == TRACE_TYPE_PARTIAL_LINE) {
/* don't print partial lines */
- iter->seq.seq.len = len;
+ iter->seq.seq.len = save_len;
break;
}
if (ret != TRACE_TYPE_NO_CONSUME)
trace_consume(iter);
- if (iter->seq.seq.len >= cnt)
+ if (trace_seq_used(&iter->seq) >= cnt)
break;
/*
@@ -4541,7 +4541,7 @@
/* Now copy what we have to the user */
sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
- if (iter->seq.seq.readpos >= iter->seq.seq.len)
+ if (iter->seq.seq.readpos >= trace_seq_used(&iter->seq))
trace_seq_init(&iter->seq);
/*
@@ -4598,7 +4598,7 @@
break;
}
- count = iter->seq.seq.len - save_len;
+ count = trace_seq_used(&iter->seq) - save_len;
if (rem < count) {
rem = 0;
iter->seq.seq.len = save_len;
@@ -4682,13 +4682,13 @@
/* Copy the data into the page, so we can start over. */
ret = trace_seq_to_buffer(&iter->seq,
page_address(spd.pages[i]),
- iter->seq.seq.len);
+ trace_seq_used(&iter->seq));
if (ret < 0) {
__free_page(spd.pages[i]);
break;
}
spd.partial[i].offset = 0;
- spd.partial[i].len = iter->seq.seq.len;
+ spd.partial[i].len = trace_seq_used(&iter->seq);
trace_seq_init(&iter->seq);
}
@@ -5689,7 +5689,8 @@
cnt = ring_buffer_read_events_cpu(trace_buf->buffer, cpu);
trace_seq_printf(s, "read events: %ld\n", cnt);
- count = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->seq.len);
+ count = simple_read_from_buffer(ubuf, count, ppos,
+ s->buffer, trace_seq_used(s));
kfree(s);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 4d0067d..935cbea 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1044,7 +1044,8 @@
mutex_unlock(&event_mutex);
if (file)
- r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->seq.len);
+ r = simple_read_from_buffer(ubuf, cnt, ppos,
+ s->buffer, trace_seq_used(s));
kfree(s);
@@ -1210,7 +1211,8 @@
trace_seq_init(s);
print_subsystem_event_filter(system, s);
- r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->seq.len);
+ r = simple_read_from_buffer(ubuf, cnt, ppos,
+ s->buffer, trace_seq_used(s));
kfree(s);
@@ -1265,7 +1267,8 @@
trace_seq_init(s);
func(s);
- r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->seq.len);
+ r = simple_read_from_buffer(ubuf, cnt, ppos,
+ s->buffer, trace_seq_used(s));
kfree(s);
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 6d1342a..ec35468 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -1153,6 +1153,9 @@
return ret;
}
+ if (trace_seq_has_overflowed(s))
+ goto out;
+
/* Strip ending newline */
if (s->buffer[s->seq.len - 1] == '\n') {
s->buffer[s->seq.len - 1] = '\0';
@@ -1160,7 +1163,7 @@
}
trace_seq_puts(s, " */\n");
-
+ out:
return trace_handle_return(s);
}
diff --git a/kernel/trace/trace_seq.c b/kernel/trace/trace_seq.c
index 74cacc93..f8b45d8 100644
--- a/kernel/trace/trace_seq.c
+++ b/kernel/trace/trace_seq.c
@@ -30,7 +30,7 @@
#define TRACE_SEQ_BUF_LEFT(s) seq_buf_buffer_left(&(s)->seq)
/* How much buffer is written? */
-#define TRACE_SEQ_BUF_USED(s) min((s)->seq.len, (unsigned int)(PAGE_SIZE - 1))
+#define TRACE_SEQ_BUF_USED(s) seq_buf_used(&(s)->seq)
/*
* trace_seq should work with being initialized with 0s.