ice: avoid undefined behavior

When writing the driver's struct ice_tlan_ctx structure, do not write the
8-bit element int_q_state with the associated internal-to-hardware field
which is 122-bits, otherwise the helper function ice_write_byte() will use
undefined behavior when setting the mask used for that write.  This should
not cause any functional change and will avoid use of undefined behavior.
Also, update a comment to highlight this structure element is not written.

Signed-off-by: Bruce Allan <[email protected]>
Signed-off-by: Tony Nguyen <[email protected]>
Tested-by: Andrew Bowers <[email protected]>
Signed-off-by: Jeff Kirsher <[email protected]>

drivers/net/ethernet/intel/ice/ice_base.c

@@ -638,6 +638,7 @@ ice_vsi_cfg_txq(struct ice_vsi *vsi, struct ice_ring *ring,
 	struct ice_aqc_add_txqs_perq *txq;
 	struct ice_pf *pf = vsi->back;
 	u8 buf_len = sizeof(*qg_buf);
+	struct ice_hw *hw = &pf->hw;
 	enum ice_status status;
 	u16 pf_q;
 	u8 tc;
@@ -646,13 +647,13 @@ ice_vsi_cfg_txq(struct ice_vsi *vsi, struct ice_ring *ring,
 	ice_setup_tx_ctx(ring, &tlan_ctx, pf_q);
 	/* copy context contents into the qg_buf */
 	qg_buf->txqs[0].txq_id = cpu_to_le16(pf_q);
-	ice_set_ctx((u8 *)&tlan_ctx, qg_buf->txqs[0].txq_ctx,
+	ice_set_ctx(hw, (u8 *)&tlan_ctx, qg_buf->txqs[0].txq_ctx,
 		    ice_tlan_ctx_info);
 
 	/* init queue specific tail reg. It is referred as
 	 * transmit comm scheduler queue doorbell.
 	 */
-	ring->tail = pf->hw.hw_addr + QTX_COMM_DBELL(pf_q);
+	ring->tail = hw->hw_addr + QTX_COMM_DBELL(pf_q);
 
 	if (IS_ENABLED(CONFIG_DCB))
 		tc = ring->dcb_tc;

drivers/net/ethernet/intel/ice/ice_common.c

@@ -1098,7 +1098,7 @@ ice_write_rxq_ctx(struct ice_hw *hw, struct ice_rlan_ctx *rlan_ctx,
 
 	rlan_ctx->prefena = 1;
 
-	ice_set_ctx((u8 *)rlan_ctx, ctx_buf, ice_rlan_ctx_info);
+	ice_set_ctx(hw, (u8 *)rlan_ctx, ctx_buf, ice_rlan_ctx_info);
 	return ice_copy_rxq_ctx_to_hw(hw, ctx_buf, rxq_index);
 }
 
@@ -3199,12 +3199,14 @@ ice_write_qword(u8 *src_ctx, u8 *dest_ctx, const struct ice_ctx_ele *ce_info)
 
 /**
  * ice_set_ctx - set context bits in packed structure
+ * @hw: pointer to the hardware structure
  * @src_ctx:  pointer to a generic non-packed context structure
  * @dest_ctx: pointer to memory for the packed structure
  * @ce_info:  a description of the structure to be transformed
  */
 enum ice_status
-ice_set_ctx(u8 *src_ctx, u8 *dest_ctx, const struct ice_ctx_ele *ce_info)
+ice_set_ctx(struct ice_hw *hw, u8 *src_ctx, u8 *dest_ctx,
+	    const struct ice_ctx_ele *ce_info)
 {
 	int f;
 
@@ -3213,6 +3215,12 @@ ice_set_ctx(u8 *src_ctx, u8 *dest_ctx, const struct ice_ctx_ele *ce_info)
 		 * using the correct size so that we are correct regardless
 		 * of the endianness of the machine.
 		 */
+		if (ce_info[f].width > (ce_info[f].size_of * BITS_PER_BYTE)) {
+			ice_debug(hw, ICE_DBG_QCTX,
+				  "Field %d width of %d bits larger than size of %d byte(s) ... skipping write\n",
+				  f, ce_info[f].width, ce_info[f].size_of);
+			continue;
+		}
 		switch (ce_info[f].size_of) {
 		case sizeof(u8):
 			ice_write_byte(src_ctx, dest_ctx, &ce_info[f]);

drivers/net/ethernet/intel/ice/ice_common.h

@@ -70,7 +70,8 @@ enum ice_status ice_aq_q_shutdown(struct ice_hw *hw, bool unloading);
 void ice_fill_dflt_direct_cmd_desc(struct ice_aq_desc *desc, u16 opcode);
 extern const struct ice_ctx_ele ice_tlan_ctx_info[];
 enum ice_status
-ice_set_ctx(u8 *src_ctx, u8 *dest_ctx, const struct ice_ctx_ele *ce_info);
+ice_set_ctx(struct ice_hw *hw, u8 *src_ctx, u8 *dest_ctx,
+	    const struct ice_ctx_ele *ce_info);
 
 extern struct mutex ice_global_cfg_lock_sw;
 

drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h

@@ -581,7 +581,7 @@ struct ice_tlan_ctx {
 	u8 drop_ena;
 	u8 cache_prof_idx;
 	u8 pkt_shaper_prof_idx;
-	u8 int_q_state;	/* width not needed - internal do not write */
+	u8 int_q_state;	/* width not needed - internal - DO NOT WRITE!!! */
 };
 
 /* macro to make the table lines short */