On Fri, Sep 01, 2023 at 08:02:17PM +0200, mwilck@xxxxxxxx wrote:
> From: Martin Wilck <mwilck@xxxxxxxx>
>
> If the bindings file is changed in a way that multipathd can't handle
> (e.g. by swapping the aliases of two maps), multipathd must not try
> to re-use an alias that is already used by another map. Creating
> or renaming a map with such an alias will fail. We already avoid
> this for some cases, but not for all. Fix it.
>
> Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
> Cc: David Bond <dbond@xxxxxxxx>
> ---
> libmultipath/alias.c | 36 +++++++++++++++++++++++++++++++-----
> tests/alias.c | 2 +-
> 2 files changed, 32 insertions(+), 6 deletions(-)
>
> diff --git a/libmultipath/alias.c b/libmultipath/alias.c
> index 9b9b789..f7834d1 100644
> --- a/libmultipath/alias.c
> +++ b/libmultipath/alias.c
> @@ -120,7 +120,7 @@ static bool alias_already_taken(const char *alias, const char *map_wwid)
> if (dm_get_uuid(alias, wwid, sizeof(wwid)) == 0 &&
> strncmp(map_wwid, wwid, sizeof(wwid)) == 0)
> return false;
> - condlog(3, "%s: alias '%s' already taken, but not in bindings file. reselecting alias",
> + condlog(3, "%s: alias '%s' already taken, reselecting alias",
> map_wwid, alias);
> return true;
> }
> @@ -363,28 +363,54 @@ char *get_user_friendly_alias(const char *wwid, const char *file, const char *al
> * allocated correctly
> */
> if (strcmp(buff, wwid) == 0) {
I'm confused about this. We should only have alias_old set if there
already exists a device that matches this WWID, right? That's what I
though alias_old means. Am I missing some way that alias_old could get
set to something other than the alias of an already existing device with
a matching WWID? Otherwise, once we verify that that this mapping also
exists in the bindings file, we should be fine to use it?
> - alias = strdup(alias_old);
> + if (!alias_already_taken(alias_old, wwid))
> + alias = strdup(alias_old);
> + else
> + condlog(0, "ERROR: old alias [%s] for wwid [%s] is used by other map",
> + alias_old, wwid);
> goto out;
> +
> } else {
> condlog(0, "alias %s already bound to wwid %s, cannot reuse",
> alias_old, buff);
> - goto new_alias;
extra semicolon.
> + goto new_alias; ;
> }
> }
>
> + /*
> + * Look for an existing alias in the bindings file.
> + * Pass prefix = NULL, so lookup_binding() won't try to allocate a new id.
> + */
There's no point in saving the return value here. We don't use if for
anything.
> id = lookup_binding(f, wwid, &alias, NULL, 0);
> if (alias) {
> - condlog(3, "Use existing binding [%s] for WWID [%s]",
> - alias, wwid);
> + if (alias_already_taken(alias, wwid)) {
> + free(alias);
> + alias = NULL;
> + } else
> + condlog(3, "Use existing binding [%s] for WWID [%s]",
> + alias, wwid);
> goto out;
> }
>
> /* allocate the existing alias in the bindings file */
> id = scan_devname(alias_old, prefix);
Again, unless I'm overlooking something, I don't think we need to
check if the alias is already taken here. Since we know that a device
already exists with alias_old and the correct WWID, as long as alias_old
is a valid user_friendly_name we can just use it.
> + if (id > 0 && id_already_taken(id, prefix, wwid)) {
> + condlog(0, "ERROR: old alias [%s] for wwid [%s] is used by other map",
> + alias_old, wwid);
> + goto out;
> + }
>
> new_alias:
> if (id <= 0) {
> + /*
> + * no existing alias was provided, or allocating it
> + * failed. Try a new one.
> + */
> id = lookup_binding(f, wwid, &alias, prefix, 1);
If lookup_binding() was going to return (id == 0) it already would have
when we called it earlier in this function, so I don't think this check
is necessary either.
-Ben
> + if (id == 0 && alias_already_taken(alias, wwid)) {
> + free(alias);
> + alias = NULL;
> + }
> if (id <= 0)
> goto out;
> else
> diff --git a/tests/alias.c b/tests/alias.c
> index 3ca6c28..11f209e 100644
> --- a/tests/alias.c
> +++ b/tests/alias.c
> @@ -398,7 +398,7 @@ static void mock_self_alias(const char *alias, const char *wwid)
> will_return(__wrap_dm_get_uuid, wwid);
> }
>
> -#define USED_STR(alias_str, wwid_str) wwid_str ": alias '" alias_str "' already taken, but not in bindings file. reselecting alias\n"
> +#define USED_STR(alias_str, wwid_str) wwid_str ": alias '" alias_str "' already taken, reselecting alias\n"
>
> static void mock_failed_alias(const char *alias, char *msg)
> {
> --
> 2.41.0
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