[PATCH v3] drivers/edac/edac_mc: Remove all strcpy() uses

[Len Baker]

strcpy() performs no bounds checking on the destination buffer. This
could result in linear overflows beyond the end of the buffer, leading
to all kinds of misbehaviors. The safe replacement is strscpy().

This is a previous step in the path to remove the strcpy() function
entirely from the kernel.

Signed-off-by: Len Baker <len.baker@xxxxxxx>
---
This is a task of the KSPP [1]

[1] https://github.com/KSPP/linux/issues/88

Changelog v1 -> v2
- Use the strscpy() instead of scnprintf() to add labels and follow a
  code pattern more similar to the current one (advance "p" and
  decrement "left") (Robert Richter).

Changelog v2 -> v3
- Rename the "left" variable to "len" (Robert Richter).
- Use strlen(p) instead of strlen(OTHER_LABEL) to decrement "len" and
  increment "p" as otherwise "left" could underflow and p overflow
  (Robert Richter).

Previous versions:

v1
https://lore.kernel.org/linux-hardening/20210725162954.9861-1-len.baker@xxxxxxx/

v2
https://lore.kernel.org/linux-hardening/20210801143558.12674-1-len.baker@xxxxxxx/

 drivers/edac/edac_mc.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
index f6d462d0be2d..0cdb1e9320ba 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -1032,6 +1032,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
 	int i, n_labels = 0;
 	struct edac_raw_error_desc *e = &mci->error_desc;
 	bool any_memory = true;
+	size_t len;

 	edac_dbg(3, "MC%d\n", mci->mc_idx);

@@ -1086,6 +1087,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
 	 */
 	p = e->label;
 	*p = '\0';
+	len = sizeof(e->label);

 	mci_for_each_dimm(mci, dimm) {
 		if (top_layer >= 0 && top_layer != dimm->location[0])
@@ -1113,11 +1115,11 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
 			p = e->label;
 			*p = '\0';
 		} else {
-			if (p != e->label) {
-				strcpy(p, OTHER_LABEL);
-				p += strlen(OTHER_LABEL);
-			}
-			strcpy(p, dimm->label);
+			const char *text = (p != e->label) ? OTHER_LABEL :
+				dimm->label;
+
+			strscpy(p, text, len);
+			len -= strlen(p);
 			p += strlen(p);
 		}

@@ -1140,9 +1142,9 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
 	}

 	if (any_memory)
-		strcpy(e->label, "any memory");
+		strscpy(e->label, "any memory", sizeof(e->label));
 	else if (!*e->label)
-		strcpy(e->label, "unknown memory");
+		strscpy(e->label, "unknown memory", sizeof(e->label));

 	edac_inc_csrow(e, row, chan);

--
2.25.1