smb2_readv_callback(struct mid_q_entry *mid)
{
	struct cifs_readdata *rdata = mid->callback_data;
	struct cifs_tcon *tcon = tlink_tcon(rdata->cfile->tlink);
	struct TCP_Server_Info *server = tcon->ses->server;
	struct smb2_sync_hdr *shdr =
				(struct smb2_sync_hdr *)rdata->iov[0].iov_base;
	struct cifs_credits credits = { .value = 0, .instance = 0 };
	struct smb_rqst rqst = { .rq_iov = rdata->iov,
				 .rq_nvec = 2,
				 .rq_pages = rdata->pages,
				 .rq_offset = rdata->page_offset,
				 .rq_npages = rdata->nr_pages,
				 .rq_pagesz = rdata->pagesz,
				 .rq_tailsz = rdata->tailsz };

	cifs_dbg(FYI, "%s: mid=%llu state=%d result=%d bytes=%u\n",
		 __func__, mid->mid, mid->mid_state, rdata->result,
		 rdata->bytes);

	switch (mid->mid_state) {
	case MID_RESPONSE_RECEIVED:
		credits.value = le16_to_cpu(shdr->CreditRequest);
		credits.instance = server->reconnect_instance;
		/* result already set, check signature */
		if (server->sign && !mid->decrypted) {
			int rc;

			rc = smb2_verify_signature(&rqst, server);
			if (rc)
				cifs_dbg(VFS, "SMB signature verification returned error = %d\n",
					 rc);
		}
		/* FIXME: should this be counted toward the initiating task? */
		task_io_account_read(rdata->got_bytes);
		cifs_stats_bytes_read(tcon, rdata->got_bytes);
		break;
	case MID_REQUEST_SUBMITTED:
	case MID_RETRY_NEEDED:
		rdata->result = -EAGAIN;
		if (server->sign && rdata->got_bytes)
			/* reset bytes number since we can not check a sign */
			rdata->got_bytes = 0;
		/* FIXME: should this be counted toward the initiating task? */
		task_io_account_read(rdata->got_bytes);
		cifs_stats_bytes_read(tcon, rdata->got_bytes);
		break;
	case MID_RESPONSE_MALFORMED:
		credits.value = le16_to_cpu(shdr->CreditRequest);
		credits.instance = server->reconnect_instance;
		/* fall through */
	default:
		rdata->result = -EIO;
	}
#ifdef CONFIG_CIFS_SMB_DIRECT
	/*
	 * If this rdata has a memmory registered, the MR can be freed
	 * MR needs to be freed as soon as I/O finishes to prevent deadlock
	 * because they have limited number and are used for future I/Os
	 */
	if (rdata->mr) {
		smbd_deregister_mr(rdata->mr);
		rdata->mr = NULL;
	}
#endif
	if (rdata->result && rdata->result != -ENODATA) {
		cifs_stats_fail_inc(tcon, SMB2_READ_HE);
		trace_smb3_read_err(0 /* xid */,
				    rdata->cfile->fid.persistent_fid,
				    tcon->tid, tcon->ses->Suid, rdata->offset,
				    rdata->bytes, rdata->result);
	} else
		trace_smb3_read_done(0 /* xid */,
				     rdata->cfile->fid.persistent_fid,
				     tcon->tid, tcon->ses->Suid,
				     rdata->offset, rdata->got_bytes);

	queue_work(cifsiod_wq, &rdata->work);
	DeleteMidQEntry(mid);
	add_credits(server, &credits, 0);
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.