IB/isert: Fix unaligned immediate-data handling

Currently we allocate rx buffers in a single contiguous buffers for
headers (iser and iscsi) and data trailer. This means that most likely the
data starting offset is aligned to 76 bytes (size of both headers).

This worked fine for years, but at some point this broke, resulting in
data corruptions in isert when a command comes with immediate data and the
underlying backend device assumes 512 bytes buffer alignment.

We assume a hard-requirement for all direct I/O buffers to be 512 bytes
aligned. To fix this, we should avoid passing unaligned buffers for I/O.

Instead, we allocate our recv buffers with some extra space such that we
can have the data portion align to 512 byte boundary. This also means that
we cannot reference headers or data using structure but rather
accessors (as they may move based on alignment). Also, get rid of the
wrong __packed annotation from iser_rx_desc as this has only harmful
effects (not aligned to anything).

This affects the rx descriptors for iscsi login and data plane.

Fixes: 3d75ca0adef4 ("block: introduce multi-page bvec helpers")
Link: https://lore.kernel.org/r/20200904195039.31687-1-sagi@grimberg.me
Reported-by: Stephen Rust <srust@blockbridge.com>
Tested-by: Doug Dumitru <doug@dumitru.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

1 files changed, 31 insertions, 10 deletions

diff --git a/drivers/infiniband/ulp/isert/ib_isert.h b/drivers/infiniband/ulp/isert/ib_isert.h
index c55f7d9bfced..7fee4a65e181 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.h
+++ b/drivers/infiniband/ulp/isert/ib_isert.h
@@ -59,9 +59,11 @@
 				ISERT_MAX_TX_MISC_PDUS	+ \
 				ISERT_MAX_RX_MISC_PDUS)
 
-#define ISER_RX_PAD_SIZE	(ISCSI_DEF_MAX_RECV_SEG_LEN + 4096 - \
-		(ISER_RX_PAYLOAD_SIZE + sizeof(u64) + sizeof(struct ib_sge) + \
-		 sizeof(struct ib_cqe) + sizeof(bool)))
+/*
+ * RX size is default of 8k plus headers, but data needs to align to
+ * 512 boundary, so use 1024 to have the extra space for alignment.
+ */
+#define ISER_RX_SIZE		(ISCSI_DEF_MAX_RECV_SEG_LEN + 1024)
 
 /* Maximum support is 16MB I/O size */
 #define ISCSI_ISER_MAX_SG_TABLESIZE	4096
@@ -81,21 +83,41 @@ enum iser_conn_state {
 };
 
 struct iser_rx_desc {
-	struct iser_ctrl iser_header;
-	struct iscsi_hdr iscsi_header;
-	char		data[ISCSI_DEF_MAX_RECV_SEG_LEN];
+	char		buf[ISER_RX_SIZE];
 	u64		dma_addr;
 	struct ib_sge	rx_sg;
 	struct ib_cqe	rx_cqe;
 	bool		in_use;
-	char		pad[ISER_RX_PAD_SIZE];
-} __packed;
+};
 
 static inline struct iser_rx_desc *cqe_to_rx_desc(struct ib_cqe *cqe)
 {
 	return container_of(cqe, struct iser_rx_desc, rx_cqe);
 }
 
+static void *isert_get_iser_hdr(struct iser_rx_desc *desc)
+{
+	return PTR_ALIGN(desc->buf + ISER_HEADERS_LEN, 512) - ISER_HEADERS_LEN;
+}
+
+static size_t isert_get_hdr_offset(struct iser_rx_desc *desc)
+{
+	return isert_get_iser_hdr(desc) - (void *)desc->buf;
+}
+
+static void *isert_get_iscsi_hdr(struct iser_rx_desc *desc)
+{
+	return isert_get_iser_hdr(desc) + sizeof(struct iser_ctrl);
+}
+
+static void *isert_get_data(struct iser_rx_desc *desc)
+{
+	void *data = isert_get_iser_hdr(desc) + ISER_HEADERS_LEN;
+
+	WARN_ON((uintptr_t)data & 511);
+	return data;
+}
+
 struct iser_tx_desc {
 	struct iser_ctrl iser_header;
 	struct iscsi_hdr iscsi_header;
@@ -142,9 +164,8 @@ struct isert_conn {
 	u32			responder_resources;
 	u32			initiator_depth;
 	bool			pi_support;
-	struct iser_rx_desc	*login_req_buf;
+	struct iser_rx_desc	*login_desc;
 	char			*login_rsp_buf;
-	u64			login_req_dma;
 	int			login_req_len;
 	u64			login_rsp_dma;
 	struct iser_rx_desc	*rx_descs;