nvme: Fix parsing of ANA log page

Check validity of offset into ANA log buffer before accessing
nvme_ana_group_desc. This check ensures the size of ANA log buffer >=
offset + sizeof(nvme_ana_group_desc)
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Signed-off-by: NPrabhath Sajeepa <psajeepa@purestorage.com>
Signed-off-by: NKeith Busch <kbusch@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

drivers/nvme/host/multipath.c

@@ -445,8 +445,14 @@ static int nvme_parse_ana_log(struct nvme_ctrl *ctrl, void *data,
 
 	for (i = 0; i < le16_to_cpu(ctrl->ana_log_buf->ngrps); i++) {
 		struct nvme_ana_group_desc *desc = base + offset;
-		u32 nr_nsids = le32_to_cpu(desc->nnsids);
-		size_t nsid_buf_size = nr_nsids * sizeof(__le32);
+		u32 nr_nsids;
+		size_t nsid_buf_size;
+
+		if (WARN_ON_ONCE(offset > ctrl->ana_log_size - sizeof(*desc)))
+			return -EINVAL;
+
+		nr_nsids = le32_to_cpu(desc->nnsids);
+		nsid_buf_size = nr_nsids * sizeof(__le32);
 
 		if (WARN_ON_ONCE(desc->grpid == 0))
 			return -EINVAL;
@@ -466,8 +472,6 @@ static int nvme_parse_ana_log(struct nvme_ctrl *ctrl, void *data,
 			return error;
 
 		offset += nsid_buf_size;
-		if (WARN_ON_ONCE(offset > ctrl->ana_log_size - sizeof(*desc)))
-			return -EINVAL;
 	}
 
 	return 0;