[LU-6869] libcfs_ukuc_msg_get() returns -errno after read() returns 0

• Type: Bug
• Resolution: Unresolved
• Priority: Minor
• Affects Version/s: Lustre 2.8.0, Lustre 2.15.0
• Severity: 3
• Assignee: WC Triage
• Reporter: John Hammond

Description

In libcfs_ukuc_msg_get() we have

int libcfs_ukuc_msg_get(struct lustre_kernelcomm *link, char *buf, int maxsize,
                        int transport)
{
        struct kuc_hdr *kuch;
        int rc = 0;

        memset(buf, 0, maxsize);

        while (1) {
                /* Read header first to get message size */
                rc = read(link->lk_rfd, buf, lhsz);
                if (rc <= 0) {
                        rc = -errno;
                        break;
                }

                ...
        }
        return rc;
}

If read() returned 0 then the contents of errno are arbitrary.