linux-kernel - [PATCH] firmware: arm_scmi: quirk: fix write to string constant

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Message-ID: <20250829132152.28218-1-johan@kernel.org>
Date: Fri, 29 Aug 2025 15:21:52 +0200
From: Johan Hovold <johan@...nel.org>
To: Sudeep Holla <sudeep.holla@....com>
Cc: Cristian Marussi <cristian.marussi@....com>,
	arm-scmi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Johan Hovold <johan@...nel.org>,
	stable@...r.kernel.org
Subject: [PATCH] firmware: arm_scmi: quirk: fix write to string constant

The quirk version range is typically a string constant and must not be
modified (e.g. as it may be stored in read-only memory):

	Unable to handle kernel write to read-only memory at virtual
	address ffffc036d998a947

Fix the range parsing so that it operates on a copy of the version range
string, and mark all the quirk strings as const to reduce the risk of
introducing similar future issues.

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220437
Fixes: 487c407d57d6 ("firmware: arm_scmi: Add common framework to handle firmware quirks")
Cc: stable@...r.kernel.org	# 6.16
Cc: Cristian Marussi <cristian.marussi@....com>
Signed-off-by: Johan Hovold <johan@...nel.org>
---
 drivers/firmware/arm_scmi/quirks.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/firmware/arm_scmi/quirks.c b/drivers/firmware/arm_scmi/quirks.c
index 03960aca3610..e70823754b0b 100644
--- a/drivers/firmware/arm_scmi/quirks.c
+++ b/drivers/firmware/arm_scmi/quirks.c
@@ -89,9 +89,9 @@
 struct scmi_quirk {
 	bool enabled;
 	const char *name;
-	char *vendor;
-	char *sub_vendor_id;
-	char *impl_ver_range;
+	const char *vendor;
+	const char *sub_vendor_id;
+	const char *impl_ver_range;
 	u32 start_range;
 	u32 end_range;
 	struct static_key_false *key;
@@ -217,7 +217,7 @@ static unsigned int scmi_quirk_signature(const char *vend, const char *sub_vend)
 
 static int scmi_quirk_range_parse(struct scmi_quirk *quirk)
 {
-	const char *last, *first = quirk->impl_ver_range;
+	const char *last, *first;
 	size_t len;
 	char *sep;
 	int ret;
@@ -228,8 +228,12 @@ static int scmi_quirk_range_parse(struct scmi_quirk *quirk)
 	if (!len)
 		return 0;
 
+	first = kmemdup(quirk->impl_ver_range, len + 1, GFP_KERNEL);
+	if (!first)
+		return -ENOMEM;
+
 	last = first + len - 1;
-	sep = strchr(quirk->impl_ver_range, '-');
+	sep = strchr(first, '-');
 	if (sep)
 		*sep = '\0';
 
@@ -238,7 +242,7 @@ static int scmi_quirk_range_parse(struct scmi_quirk *quirk)
 	else /* X OR X- OR X-y */
 		ret = kstrtouint(first, 0, &quirk->start_range);
 	if (ret)
-		return ret;
+		goto out_free;
 
 	if (!sep)
 		quirk->end_range = quirk->start_range;
@@ -246,7 +250,9 @@ static int scmi_quirk_range_parse(struct scmi_quirk *quirk)
 		ret = kstrtouint(sep + 1, 0, &quirk->end_range);
 
 	if (quirk->start_range > quirk->end_range)
-		return -EINVAL;
+		ret = -EINVAL;
+out_free:
+	kfree(first);
 
 	return ret;
 }
-- 
2.49.1