[PATCH 5.5 029/257] EDAC/mc: Report "unknown memory" on too many DIMM labels found

[Greg Kroah-Hartman]

From: Robert Richter <rrichter@xxxxxxxxxxx>

[ Upstream commit 65bb4d1af92cf007adc0a0c59dadcc393c5cada6 ]

There is a limitation to report only EDAC_MAX_LABELS in e->label of
the error descriptor. This is to prevent a potential string overflow.

The current implementation falls back to "any memory" in this case and
also stops all further processing to find a unique row and channel of
the possible error location.

Reporting "any memory" is wrong as the memory controller reported an
error location for one of the layers. Instead, report "unknown memory"
and also do not break early in the loop to further check row and channel
for uniqueness.

 [ bp: Massage commit message. ]

Signed-off-by: Robert Richter <rrichter@xxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Acked-by: Aristeu Rozanski <aris@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200123090210.26933-7-rrichter@xxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/edac/edac_mc.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
index 69e0d90460e6c..2349f2ad946bb 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -1180,20 +1180,21 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
 		 * channel/memory controller/...  may be affected.
 		 * Also, don't show errors for empty DIMM slots.
 		 */
-		if (!e->enable_per_layer_report || !dimm->nr_pages)
+		if (!dimm->nr_pages)
 			continue;
 
-		if (n_labels >= EDAC_MAX_LABELS) {
-			e->enable_per_layer_report = false;
-			break;
-		}
 		n_labels++;
-		if (p != e->label) {
-			strcpy(p, OTHER_LABEL);
-			p += strlen(OTHER_LABEL);
+		if (n_labels > EDAC_MAX_LABELS) {
+			p = e->label;
+			*p = '\0';
+		} else {
+			if (p != e->label) {
+				strcpy(p, OTHER_LABEL);
+				p += strlen(OTHER_LABEL);
+			}
+			strcpy(p, dimm->label);
+			p += strlen(p);
 		}
-		strcpy(p, dimm->label);
-		p += strlen(p);
 
 		/*
 		 * get csrow/channel of the DIMM, in order to allow
-- 
2.20.1