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scd: Add explict functions for 'app' reference counting.

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* scd/app.c (app_ref): New.
(app_unref): New.
(release_application): Renamed to ...
(app_unref_locked): this and remove arg locked_already.  Change
callers to use this or app_ref.
* scd/command.c (open_card_with_request):
(cmd_pksign, cmd_pkauth, cmd_pkdecrypt): Use app_ref and app_unref
instead of accessing the counter directly.
--

This is better in case we need to debug stuff.  There is a real change
however: We now lock and unlock the app before changing the reference
count.

The whole app locking business should be reviewed because we pass
pointers along without immediately bumping the refcount.

Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2019-06-17 16:19:22 +02:00
parent 70f7b26287
commit c594dcfc93
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GPG key ID: E3FDFF218E45B72B
4 changed files with 55 additions and 23 deletions
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48
scd/app.c
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@ -242,7 +242,7 @@ app_reset (app_t app, ctrl_t ctrl, int send_reset)
else
{
ctrl->app_ctx = NULL;
release_application (app, 0);
app_unref (app);
}
return err;
@ -541,6 +541,7 @@ select_application (ctrl_t ctrl, const char *name, app_t *r_app,
err = check_conflict (a, name);
if (!err)
{
/* Note: We do not use app_ref as we are already locked. */
a->ref_count++;
*r_app = a;
if (a_prev)
@ -604,7 +605,8 @@ deallocate_app (app_t app)
a_prev = a;
if (app->ref_count)
log_error ("trying to release context used yet (%d)\n", app->ref_count);
log_error ("trying to release still used app context (%d)\n",
app->ref_count);
if (app->fnc.deinit)
{
@ -618,13 +620,24 @@ deallocate_app (app_t app)
xfree (app);
}
/* Free the resources associated with the application APP. APP is
allowed to be NULL in which case this is a no-op. Note that we are
using reference counting to track the users of the application and
actually deferring the deallocation to allow for a later reuse by
a new connection. */
/* Increment the reference counter for APP. Returns the APP. */
app_t
app_ref (app_t app)
{
lock_app (app, NULL);
++app->ref_count;
unlock_app (app);
return app;
}
/* Decrement the reference counter for APP. Note that we are using
* reference counting to track the users of the application and are
* deferring the actual deallocation to allow for a later reuse by a
* new connection. Using NULL for APP is a no-op. */
void
release_application (app_t app, int locked_already)
app_unref (app_t app)
{
if (!app)
return;
@ -634,15 +647,26 @@ release_application (app_t app, int locked_already)
is using the card - this way the PIN cache and other cached data
are preserved. */
if (!locked_already)
lock_app (app, NULL);
lock_app (app, NULL);
if (!app->ref_count)
log_bug ("trying to release an already released context\n");
--app->ref_count;
unlock_app (app);
}
/* This is the same as app_unref but assumes that APP is already
* locked. */
void
app_unref_locked (app_t app)
{
if (!app)
return;
if (!app->ref_count)
log_bug ("trying to release an already released context\n");
--app->ref_count;
if (!locked_already)
unlock_app (app);
}