[systemd-devel] [PATCH 2/2] detect-virt: dmi: fix mem leak

[Lennart Poettering]

On Tue, 03.11.15 15:04, Andrew Jones (drjones at redhat.com) wrote:

> The variable 's' is still in scope until we exit the function. We
> can't call read_one_line_file on it multiple times without calling
> free in between.
> ---
>  src/basic/virt.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/src/basic/virt.c b/src/basic/virt.c
> index 1e10fc755f201..f88bd04bd72ed 100644
> --- a/src/basic/virt.c
> +++ b/src/basic/virt.c
> @@ -176,9 +176,10 @@ static int detect_vm_dmi(void) {
>  
>                  r = read_one_line_file(dmi_vendors[i], &s);
>                  if (r < 0) {
> -                        if (r == -ENOENT)
> +                        if (r == -ENOENT) {
> +                                free(s);
>                                  continue;

Note that we use the _cleanup_free_ macro on "s", which uses gcc's
"cleanup" attribute to automatically free the variable when it goes
out of scope. An explicit free() is hence unnecessary. In fact, it
would result in a double-free.

We use the "cleanup" logic pretty much everywhere in systemd, in order
to keep the error paths manageable.

Lennart

-- 
Lennart Poettering, Red Hat