[apparmor] [bug report] AppArmor: Add selfattr hooks

[Dan Carpenter]

Hello Casey Schaufler,

The patch 3c3bda37ca1d: "AppArmor: Add selfattr hooks" from Sep 12,
2023 (linux-next), leads to the following Smatch static checker
warning:

	security/apparmor/lsm.c:817 apparmor_getselfattr()
	error: uninitialized symbol 'value'.

security/apparmor/lsm.c
    779 static int apparmor_getselfattr(unsigned int attr, struct lsm_ctx __user *lx,
    780                                 size_t *size, u32 flags)
    781 {
    782         int error = -ENOENT;
    783         struct aa_task_ctx *ctx = task_ctx(current);
    784         struct aa_label *label = NULL;
    785         size_t total_len = 0;
    786         char *value;
    787 
    788         switch (attr) {
    789         case LSM_ATTR_CURRENT:
    790                 label = aa_get_newest_label(cred_label(current_cred()));
    791                 break;
    792         case LSM_ATTR_PREV:
    793                 if (ctx->previous)
    794                         label = aa_get_newest_label(ctx->previous);
    795                 break;
    796         case LSM_ATTR_EXEC:
    797                 if (ctx->onexec)
    798                         label = aa_get_newest_label(ctx->onexec);
    799                 break;
    800         default:
    801                 error = -EOPNOTSUPP;
    802                 break;
    803         }
    804 
    805         if (label) {
    806                 error = aa_getprocattr(label, &value, false);

"value" is uninitialized on the first -EACCESS error path.

    807                 if (error > 0) {
    808                         total_len = ALIGN(struct_size(lx, ctx, error), 8);
    809                         if (total_len > *size)
    810                                 error = -E2BIG;
    811                         else if (lx)
    812                                 error = lsm_fill_user_ctx(lx, value, error,
    813                                                           LSM_ID_APPARMOR, 0);
    814                         else
    815                                 error = 1;
    816                 }
--> 817                 kfree(value);
                              ^^^^^
Uninitialized

    818         }
    819 
    820         aa_put_label(label);
    821 
    822         *size = total_len;
    823         if (error < 0)
    824                 return error;
    825         return 1;
    826 }

regards,
dan carpenter