Passing a NULL buffer into the lsm_get_self_attr() syscall is a valid
way to quickly determine the minimum size of the buffer needed to for
the syscall to return all of the LSM attributes to the caller.
Unfortunately we/I broke that behavior in commit
d7cf3412a9f6
("lsm: consolidate buffer size handling into lsm_fill_user_ctx()")
such that it returned an error to the caller; this patch restores the
original desired behavior of using the NULL buffer as a quick way to
correctly size the attribute buffer.
Cc: stable@vger.kernel.org
Fixes: d7cf3412a9f6 ("lsm: consolidate buffer size handling into lsm_fill_user_ctx()")
Signed-off-by: Paul Moore <paul@paul-moore.com>
* @id: LSM id
* @flags: LSM defined flags
*
- * Fill all of the fields in a userspace lsm_ctx structure.
+ * Fill all of the fields in a userspace lsm_ctx structure. If @uctx is NULL
+ * simply calculate the required size to output via @utc_len and return
+ * success.
*
* Returns 0 on success, -E2BIG if userspace buffer is not large enough,
* -EFAULT on a copyout error, -ENOMEM if memory can't be allocated.
goto out;
}
+ /* no buffer - return success/0 and set @uctx_len to the req size */
+ if (!uctx)
+ goto out;
+
nctx = kzalloc(nctx_len, GFP_KERNEL);
if (nctx == NULL) {
rc = -ENOMEM;