linux-kernel - [PATCH 4.19 20/73] tracing: Avoid memory leak in predicate

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Date:   Fri,  7 Jun 2019 17:39:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+6b8e0fb820e570c59e19@...kaller.appspotmail.com,
        Tomas Bortoli <tomasbortoli@...il.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 4.19 20/73] tracing: Avoid memory leak in predicate_parse()

From: Tomas Bortoli <tomasbortoli@...il.com>

commit dfb4a6f2191a80c8b790117d0ff592fd712d3296 upstream.

In case of errors, predicate_parse() goes to the out_free label
to free memory and to return an error code.

However, predicate_parse() does not free the predicates of the
temporary prog_stack array, thence leaking them.

Link: http://lkml.kernel.org/r/20190528154338.29976-1-tomasbortoli@gmail.com

Cc: stable@...r.kernel.org
Fixes: 80765597bc587 ("tracing: Rewrite filter logic to be simpler and faster")
Reported-by: syzbot+6b8e0fb820e570c59e19@...kaller.appspotmail.com
Signed-off-by: Tomas Bortoli <tomasbortoli@...il.com>
[ Added protection around freeing prog_stack[i].pred ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/trace/trace_events_filter.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -427,7 +427,7 @@ predicate_parse(const char *str, int nr_
 	op_stack = kmalloc_array(nr_parens, sizeof(*op_stack), GFP_KERNEL);
 	if (!op_stack)
 		return ERR_PTR(-ENOMEM);
-	prog_stack = kmalloc_array(nr_preds, sizeof(*prog_stack), GFP_KERNEL);
+	prog_stack = kcalloc(nr_preds, sizeof(*prog_stack), GFP_KERNEL);
 	if (!prog_stack) {
 		parse_error(pe, -ENOMEM, 0);
 		goto out_free;
@@ -576,7 +576,11 @@ predicate_parse(const char *str, int nr_
 out_free:
 	kfree(op_stack);
 	kfree(inverts);
-	kfree(prog_stack);
+	if (prog_stack) {
+		for (i = 0; prog_stack[i].pred; i++)
+			kfree(prog_stack[i].pred);
+		kfree(prog_stack);
+	}
 	return ERR_PTR(ret);
 }