Re: [PATCH] tracing: fix double free

From: Zanussi, Tom
Date: Tue Sep 08 2020 - 15:18:32 EST

Hi Tom,

On 9/7/2020 8:58 AM, trix@xxxxxxxxxx wrote:
From: Tom Rix <trix@xxxxxxxxxx>

clang static analyzer reports this problem

trace_events_hist.c:3824:3: warning: Attempt to free
released memory

In parse_var_defs() if there is a problem allocating
var_defs.expr, the earlier 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().

Fixes: 30350d65ac56 ("tracing: Add variable support to hist triggers")
Signed-off-by: Tom Rix <trix@xxxxxxxxxx>

Good catch, thanks for fixing this!

Reviewed-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>

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

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 0b933546142e..1b2ef6490229 100644
--- 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_trigger_data *hist_data)
s = kstrdup(field_str, GFP_KERNEL);
if (!s) {
- kfree(hist_data->attrs->[n_vars]);
ret = -ENOMEM;
goto free;