In the protection override dump path, the firmware can return far too
many GRC elements, resulting in attempting to write past the end of the
previously-kmalloc'ed dump buffer.

This will result in a kernel panic with reason:

 BUG: unable to handle kernel paging request at ADDRESS

where "ADDRESS" is just past the end of the protection override dump
buffer. The start address of the buffer is:
 p_hwfn->cdev->dbg_features[DBG_FEATURE_PROTECTION_OVERRIDE].dump_buf
and the size of the buffer is buf_size in the same data structure.

The panic can be arrived at from either the qede Ethernet driver path:

    [exception RIP: qed_grc_dump_addr_range+0x108]
 qed_protection_override_dump at ffffffffc02662ed [qed]
 qed_dbg_protection_override_dump at ffffffffc0267792 [qed]
 qed_dbg_feature at ffffffffc026aa8f [qed]
 qed_dbg_all_data at ffffffffc026b211 [qed]
 qed_fw_fatal_reporter_dump at ffffffffc027298a [qed]
 devlink_health_do_dump at ffffffff82497f61
 devlink_health_report at ffffffff8249cf29
 qed_report_fatal_error at ffffffffc0272baf [qed]
 qede_sp_task at ffffffffc045ed32 [qede]
 process_one_work at ffffffff81d19783

or the qedf storage driver path:

    [exception RIP: qed_grc_dump_addr_range+0x108]
 qed_protection_override_dump at ffffffffc068b2ed [qed]
 qed_dbg_protection_override_dump at ffffffffc068c792 [qed]
 qed_dbg_feature at ffffffffc068fa8f [qed]
 qed_dbg_all_data at ffffffffc0690211 [qed]
 qed_fw_fatal_reporter_dump at ffffffffc069798a [qed]
 devlink_health_do_dump at ffffffff8aa95e51
 devlink_health_report at ffffffff8aa9ae19
 qed_report_fatal_error at ffffffffc0697baf [qed]
 qed_hw_err_notify at ffffffffc06d32d7 [qed]
 qed_spq_post at ffffffffc06b1011 [qed]
 qed_fcoe_destroy_conn at ffffffffc06b2e91 [qed]
 qedf_cleanup_fcport at ffffffffc05e7597 [qedf]
 qedf_rport_event_handler at ffffffffc05e7bf7 [qedf]
 fc_rport_work at ffffffffc02da715 [libfc]
 process_one_work at ffffffff8a319663

Resolve this by clamping the firmware's return value to the maximum
number of legal elements the firmware should return.

Fixes: d52c89f120de8 ("qed*: Utilize FW 8.37.2.0")
Signed-off-by: Jamie Bainbridge <jamie.bainbridge@gmail.com>
---
v2: Move the check to the correct place after discussion with Jakub
    Kicinski and more debugging.
    Add more detail about error symptoms to the commit description
    also suggested by Jakub.
---
 drivers/net/ethernet/qlogic/qed/qed_debug.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/qlogic/qed/qed_debug.c b/drivers/net/ethernet/qlogic/qed/qed_debug.c
index 9c3d3dd2f84753100d3c639505677bd53e3ca543..1f0cea3cae92f542e0213af87e885406599980a9 100644
--- a/drivers/net/ethernet/qlogic/qed/qed_debug.c
+++ b/drivers/net/ethernet/qlogic/qed/qed_debug.c
@@ -4462,10 +4462,11 @@ static enum dbg_status qed_protection_override_dump(struct qed_hwfn *p_hwfn,
 		goto out;
 	}
 
-	/* Add override window info to buffer */
+	/* Add override window info to buffer, preventing buffer overflow */
 	override_window_dwords =
-		qed_rd(p_hwfn, p_ptt, GRC_REG_NUMBER_VALID_OVERRIDE_WINDOW) *
-		PROTECTION_OVERRIDE_ELEMENT_DWORDS;
+		min(qed_rd(p_hwfn, p_ptt, GRC_REG_NUMBER_VALID_OVERRIDE_WINDOW) *
+		PROTECTION_OVERRIDE_ELEMENT_DWORDS,
+		PROTECTION_OVERRIDE_DEPTH_DWORDS);
 	if (override_window_dwords) {
 		addr = BYTES_TO_DWORDS(GRC_REG_PROTECTION_OVERRIDE_WINDOW);
 		offset += qed_grc_dump_addr_range(p_hwfn,
-- 
2.47.3