2020-09-07 17:19:50

by Tom Rix

Subject: [PATCH] tracing: fix double free

From: Tom Rix <[email protected]>

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().

Fixes: 30350d65ac56 ("tracing: Add variable support to hist triggers")
Signed-off-by: Tom Rix <[email protected]>
---
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->var_defs.name[n_vars]);
ret = -ENOMEM;
goto free;
}
--
2.18.1

2020-09-08 19:22:32

by Tom Zanussi

Subject: Re: [PATCH] tracing: fix double free

Hi Tom,

On 9/7/2020 8:58 AM, [email protected] wrote:
> From: Tom Rix <[email protected]>
>
> 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().
>
> Fixes: 30350d65ac56 ("tracing: Add variable support to hist triggers")
> Signed-off-by: Tom Rix <[email protected]>

Good catch, thanks for fixing this!

Reviewed-by: Tom Zanussi <[email protected]>

> ---
> 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->var_defs.name[n_vars]);
> ret = -ENOMEM;
> goto free;
> }
>