[LU-4689] mds returns EINVAL for hsm commands if fsname is 8-byte aligned

• Type: Bug
• Resolution: Fixed
• Priority: Critical
• Fix Version/s: Lustre 2.6.0, Lustre 2.5.1
• Affects Version/s: Lustre 2.5.0, Lustre 2.6.0
• Labels: HSM mn4 patch
• Environment: b2_5 and master have the same issue.
• Severity: 3
• Assignee: James Nunez (Inactive)
• Reporter: Peng Tao

Description

If a filesystem name is 8-byte aligned, all HSM commands will get -EINVALID. The root cause is in following code:

/* Return pointer to first hai in action list */
static inline struct hsm_action_item *hai_first(struct hsm_action_list *hal)
{
        return (struct hsm_action_item *)(hal->hal_fsname +
                                          cfs_size_round(strlen(hal-> \
                                                                hal_fsname)));
}

hal_fsname is a string terminated with NULL. If strlen(hal->hal_fsname) is 8 aligned, hai_first() ends up eating the terminating NULL character.

Now when the caller first time call hai_first() and set proper value to the returning first hsm_action_item, it ends up appending some non-NULL characters at the address of hal_fsname + strlen(hal_fsname). The side effect is that the next time someone calls hal_first(), strlen(hal->hal_fsname) is larger than the first time. That would result in misplacement of hsm_action_item and causes hal_is_sane() check to fail.