linux-kernel - [PATCH 5.8 79/99] tracing: fix double free

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Date:   Tue, 29 Sep 2020 13:02:02 +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, Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Tom Rix <trix@...hat.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 5.8 79/99] tracing: fix double free

From: Tom Rix <trix@...hat.com>

commit 46bbe5c671e06f070428b9be142cc4ee5cedebac upstream.

clang static analyzer reports this problem

trace_events_hist.c:3824:3: warning: Attempt to free
  released memory
    kfree(hist_data->attrs->var_defs.name[i]);

In parse_var_defs() if there is a problem allocating
var_defs.expr, the earlier var_defs.name is freed.
This free is duplicated by free_var_defs() which frees
the rest of the list.

Because free_var_defs() has to run anyway, remove the
second free fom parse_var_defs().

Link: https://lkml.kernel.org/r/20200907135845.15804-1-trix@redhat.com

Cc: stable@...r.kernel.org
Fixes: 30350d65ac56 ("tracing: Add variable support to hist triggers")
Reviewed-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
Signed-off-by: Tom Rix <trix@...hat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/trace/trace_events_hist.c |    1 -
 1 file changed, 1 deletion(-)

--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -3865,7 +3865,6 @@ static int parse_var_defs(struct hist_tr
 
 			s = kstrdup(field_str, GFP_KERNEL);
 			if (!s) {
-				kfree(hist_data->attrs->var_defs.name[n_vars]);
 				ret = -ENOMEM;
 				goto free;
 			}