On Sun, Jan 10, 2021 at 01:57:26PM -0800, trix@xxxxxxxxxx wrote:
> From: Tom Rix <trix@xxxxxxxxxx>
>
> clang static analysis reports this problem
>
> rnbd-clt.c:1212:11: warning: Branch condition evaluates to a
> garbage value
> else if (!first)
> ^~~~~~
Ah, is it complaining that the 'if (IS_ERR(sess)) {' section in
find_or_create_sess() does not initialize first even though that will be
caught by the 'if (sess == ERR_PTR(-ENOMEM))' in
find_and_get_or_create_sess() because alloc_sess() only returns an
-ENOMEM error pointer?
> This is triggered in the find_and_get_or_create_sess() call
> because the variable first is not initialized and the
> earlier check is specifically for
>
> if (sess == ERR_PTR(-ENOMEM))
>
> This is false positive.
>
> But the if-check can be reduced by initializing first to
> false and then returning if the call to find_or_creat_sess()
> does not set it to true. When it remains false, either
> sess will be valid or not. The not case is caught by
> find_and_get_or_create_sess()'s caller rnbd_clt_map_device()
>
> sess = find_and_get_or_create_sess(...);
> if (IS_ERR(sess))
> return ERR_CAST(sess);
>
> Since find_and_get_or_create_sess() initializes first to false
> setting it in find_or_create_sess() is not needed.
>
> Signed-off-by: Tom Rix <trix@xxxxxxxxxx>
Every maintainer has their preference for where and how stuff gets
initialized but this makes sense to me. I am not sure the commit above
find_or_create_sess() is needed but again, personal preference.
Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
> ---
> drivers/block/rnbd/rnbd-clt.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/block/rnbd/rnbd-clt.c b/drivers/block/rnbd/rnbd-clt.c
> index 96e3f9fe8241..251f747cf10d 100644
> --- a/drivers/block/rnbd/rnbd-clt.c
> +++ b/drivers/block/rnbd/rnbd-clt.c
> @@ -919,6 +919,7 @@ static struct rnbd_clt_session *__find_and_get_sess(const char *sessname)
> return NULL;
> }
>
> +/* caller is responsible for initializing 'first' to false */
> static struct
> rnbd_clt_session *find_or_create_sess(const char *sessname, bool *first)
> {
> @@ -934,8 +935,7 @@ rnbd_clt_session *find_or_create_sess(const char *sessname, bool *first)
> }
> list_add(&sess->list, &sess_list);
> *first = true;
> - } else
> - *first = false;
> + }
> mutex_unlock(&sess_lock);
>
> return sess;
> @@ -1203,13 +1203,11 @@ find_and_get_or_create_sess(const char *sessname,
> struct rnbd_clt_session *sess;
> struct rtrs_attrs attrs;
> int err;
> - bool first;
> + bool first = false;
> struct rtrs_clt_ops rtrs_ops;
>
> sess = find_or_create_sess(sessname, &first);
> - if (sess == ERR_PTR(-ENOMEM))
> - return ERR_PTR(-ENOMEM);
> - else if (!first)
> + if (!first)
> return sess;
>
> if (!path_cnt) {
> --
> 2.27.0
>
