linux-hardening - [PATCH] drivers/edac/edac_mc: Remove all strcpy() uses

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Message-Id: <20210725162954.9861-1-len.baker@gmx.com>
Date:   Sun, 25 Jul 2021 18:29:54 +0200
From:   Len Baker <len.baker@....com>
To:     Kees Cook <keescook@...omium.org>, Borislav Petkov <bp@...en8.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        James Morse <james.morse@....com>,
        Robert Richter <rric@...nel.org>
Cc:     Len Baker <len.baker@....com>, linux-hardening@...r.kernel.org,
        linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drivers/edac/edac_mc: Remove all strcpy() uses

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().

However, to add labels is better to use the scnprintf to simplify the
arithmetic.

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

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

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

 drivers/edac/edac_mc.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
index f6d462d0be2d..1286364f0e48 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -1027,6 +1027,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
 {
 	struct dimm_info *dimm;
 	char *p;
+	size_t p_size = 0;
 	int row = -1, chan = -1;
 	int pos[EDAC_MAX_LAYERS] = { top_layer, mid_layer, low_layer };
 	int i, n_labels = 0;
@@ -1113,12 +1114,11 @@ 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);
-			p += strlen(p);
+			const char *or = (p != e->label) ? OTHER_LABEL : "";
+
+			p_size += scnprintf(p + p_size,
+					    sizeof(e->label) - p_size,
+					    "%s%s", or, dimm->label);
 		}

 		/*
@@ -1140,9 +1140,9 @@ 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