firmware: arm_scmi: quirk: Prevent writes to string constants

commit 572ce54 upstream.

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). Attempting
to do so can trigger faults such as:

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

Update 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: 487c407 ("firmware: arm_scmi: Add common framework to handle firmware quirks")
Cc: [email protected]	# 6.16
Cc: Cristian Marussi <[email protected]>
Reported-by: Jan Palus <[email protected]>
Signed-off-by: Johan Hovold <[email protected]>
Message-Id: <[email protected]>
[sudeep.holla: minor commit message rewording; switch to cleanup helpers]
Signed-off-by: Sudeep Holla <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: jhovold

drivers/firmware/arm_scmi/quirks.c

@@ -71,6 +71,7 @@
  */
 
 #include <linux/ctype.h>
+#include <linux/cleanup.h>
 #include <linux/device.h>
 #include <linux/export.h>
 #include <linux/hashtable.h>
@@ -89,9 +90,9 @@
 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 +218,7 @@ 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 __free(kfree) = NULL;
 	size_t len;
 	char *sep;
 	int ret;
@@ -228,8 +229,12 @@ 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';