Currently there are different issues associated with ftrace_enable_fops
- event_enable_write: *ppos is increased while not used at all in the
write operation itself (following a write, this could lead a read to
fail or report a corrupted event status);
- event_enable_read: cnt < strlen(buf) is allowed and this can lead to
reading an incomplete event status (i.e. not all status characters
are retrieved) and/or reading the status in a non-atomic way (i.e.
the status could change between two consecutive reads);
- .llseek is set to default_llseek: this is wrong since for this
type of files it does not make sense to reposition the ppos offset.
Hence this should be set instead to noop_llseek.
This patch fixes all the issues listed above.
Signed-off-by: Gabriele Paoloni <gpaol...@redhat.com>
Tested-by: Alessandro Carminati <acarm...@redhat.com>
---
kernel/trace/trace_events.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 120531268abf..5e84ef01d0c8 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1798,6 +1798,13 @@ event_enable_read(struct file *filp, char __user *ubuf,
size_t cnt,
strcat(buf, "\n");
+ /*
+ * A requested cnt less than strlen(buf) could lead to a wrong
+ * event status being reported.
+ */
+ if (cnt < strlen(buf))
+ return -EINVAL;
+
return simple_read_from_buffer(ubuf, cnt, ppos, buf, strlen(buf));
}
@@ -1833,8 +1840,6 @@ event_enable_write(struct file *filp, const char __user
*ubuf, size_t cnt,
return -EINVAL;
}
- *ppos += cnt;
-
return cnt;
}
@@ -2557,7 +2562,7 @@ static const struct file_operations ftrace_enable_fops = {
.read = event_enable_read,
.write = event_enable_write,
.release = tracing_release_file_tr,
- .llseek = default_llseek,
+ .llseek = noop_llseek,
};
static const struct file_operations ftrace_event_format_fops = {
--
2.48.1
