Re: [PATCH 03/11] util/selfmap: Discard mapping on error

[Eric Blake]

On Mon, Jul 12, 2021 at 02:55:27PM -0700, Richard Henderson wrote:
> From clang-13:
> util/selfmap.c:26:21: error: variable 'errors' set but not used \
>     [-Werror,-Wunused-but-set-variable]
> 
> Quite right of course, but there's no reason not to check errors.
> 
> First, incrementing errors is incorrect, because qemu_strtoul
> returns an errno not a count -- just or them together so that
> we have a non-zero value at the end.
> 
> Second, if we have an error, do not add the struct to the list,
> but free it instead.
> 
> Cc: Alex Bennée <alex.bennee@linaro.org>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  util/selfmap.c | 28 ++++++++++++++++------------
>  1 file changed, 16 insertions(+), 12 deletions(-)

> 
> diff --git a/util/selfmap.c b/util/selfmap.c
> index 2ec99dfdda..0178c2ff8b 100644
> --- a/util/selfmap.c
> +++ b/util/selfmap.c
> @@ -23,29 +23,33 @@ GSList *read_self_maps(void)
>              gchar **fields = g_strsplit(lines[i], " ", 6);
>              if (g_strv_length(fields) > 4) {
>                  MapInfo *e = g_new0(MapInfo, 1);
> -                int errors;
> +                int errors = 0;
>                  const char *end;
>  
> -                errors  = qemu_strtoul(fields[0], &end, 16, &e->start);
> -                errors += qemu_strtoul(end + 1, NULL, 16, &e->end);
> +                errors |= qemu_strtoul(fields[0], &end, 16, &e->start);
> +                errors |= qemu_strtoul(end + 1, NULL, 16, &e->end);
>  
>                  e->is_read  = fields[1][0] == 'r';
>                  e->is_write = fields[1][1] == 'w';
>                  e->is_exec  = fields[1][2] == 'x';
>                  e->is_priv  = fields[1][3] == 'p';
>  
> -                errors += qemu_strtoul(fields[2], NULL, 16, &e->offset);
> +                errors |= qemu_strtoul(fields[2], NULL, 16, &e->offset);
>                  e->dev = g_strdup(fields[3]);

e->dev now contains malloc'd memory...

> -                errors += qemu_strtou64(fields[4], NULL, 10, &e->inode);
> +                errors |= qemu_strtou64(fields[4], NULL, 10, &e->inode);

...and if this qemu_strtou64 fails...

>  
> -                /*
> -                 * The last field may have leading spaces which we
> -                 * need to strip.
> -                 */
> -                if (g_strv_length(fields) == 6) {
> -                    e->path = g_strdup(g_strchug(fields[5]));
> +                if (!errors) {
> +                    /*
> +                     * The last field may have leading spaces which we
> +                     * need to strip.
> +                     */
> +                    if (g_strv_length(fields) == 6) {
> +                        e->path = g_strdup(g_strchug(fields[5]));
> +                    }
> +                    map_info = g_slist_prepend(map_info, e);
> +                } else {
> +                    g_free(e);

...you've now leaked it.  Oops.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org