[PATCH v2] firmware_loader: Use init_utsname()->release

[John Garry]

Instead of using UTS_RELEASE, use init_utsname()->release, which means
that we don't need to rebuild the code just for the git head commit
changing.

Since UTS_RELEASE is used for fw_path[] and this points to const data,
append init_utsname()->release dynamically to an intermediate string.

The check for appending uts release is if the string in fw_path[] ends
in '/'. Since fw_path[] may include a path from the kernel command line
in fw_path_para, and it would be valid for this string to end in '/',
check for fw_path_para when appending uts release. 

Note: As mentioned by Masahiro in [0], when CONFIG_MODVERSIONS=y it
could be possible for a driver to be built as a module with a different
kernel baseline and so use a different UTS_RELEASE from that baseline. So
now using init_utsname()->release could lead to a change in behaviour
in this driver. However, considering the nature of this driver and how it
would not make sense to build it as an external module against a different
tree, this change should not have any effect on users.

[0] https://lore.kernel.org/lkml/CAK7LNAQ_r5yUjNpOppLkDBQ12sDxBYQTvRZGn1ng8D1POfZr_A@xxxxxxxxxxxxxx/

Reviewed-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
---
Changes in v2:
- moved note into commit log and tweaked slightly
- add Luis' RB tags, thanks

Also verified against fw loader selftest - it seems to show no regression
from baseline, however the baeline sometimes hangs (and also does with
this patch).

diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index 3c67f24785fc..9a3671659134 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -38,7 +38,7 @@
 #include <linux/zstd.h>
 #include <linux/xz.h>
 
-#include <generated/utsrelease.h>
+#include <linux/utsname.h>
 
 #include "../base.h"
 #include "firmware.h"
@@ -471,9 +471,9 @@ static int fw_decompress_xz(struct device *dev, struct fw_priv *fw_priv,
 static char fw_path_para[256];
 static const char * const fw_path[] = {
 	fw_path_para,
-	"/lib/firmware/updates/" UTS_RELEASE,
+	"/lib/firmware/updates/", /* UTS_RELEASE is appended later */
 	"/lib/firmware/updates",
-	"/lib/firmware/" UTS_RELEASE,
+	"/lib/firmware/", /* UTS_RELEASE is appended later */
 	"/lib/firmware"
 };
 
@@ -496,7 +496,7 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
 	size_t size;
 	int i, len, maxlen = 0;
 	int rc = -ENOENT;
-	char *path, *nt = NULL;
+	char *path, *fw_path_string, *nt = NULL;
 	size_t msize = INT_MAX;
 	void *buffer = NULL;
 	dev_err(device, "%s suffix=%s\n", __func__, suffix);
@@ -511,6 +511,12 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
 	if (!path)
 		return -ENOMEM;
 
+	fw_path_string = __getname();
+	if (!fw_path_string) {
+		__putname(path);
+		return -ENOMEM;
+	}
+
 	wait_for_initramfs();
 	for (i = 0; i < ARRAY_SIZE(fw_path); i++) {
 		size_t file_size = 0;
@@ -521,16 +527,32 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
 		if (!fw_path[i][0])
 			continue;
 
+		len = snprintf(fw_path_string, PATH_MAX, "%s", fw_path[i]);
+		if (len >= PATH_MAX) {
+			rc = -ENAMETOOLONG;
+			break;
+		}
+
+		/* Special handling to append UTS_RELEASE */
+		if ((fw_path[i] != fw_path_para) && (fw_path[i][len - 1] == '/')) {
+			len = snprintf(fw_path_string, PATH_MAX, "%s%s",
+					fw_path[i], init_utsname()->release);
+			if (len >= PATH_MAX) {
+				rc = -ENAMETOOLONG;
+				break;
+			}
+		}
+
 		/* strip off \n from customized path */
-		maxlen = strlen(fw_path[i]);
+		maxlen = strlen(fw_path_string);
 		if (i == 0) {
-			nt = strchr(fw_path[i], '\n');
+			nt = strchr(fw_path_string, '\n');
 			if (nt)
-				maxlen = nt - fw_path[i];
+				maxlen = nt - fw_path_string;
 		}
 
 		len = snprintf(path, PATH_MAX, "%.*s/%s%s",
-			       maxlen, fw_path[i],
+			       maxlen, fw_path_string,
 			       fw_priv->fw_name, suffix);
 		if (len >= PATH_MAX) {
 			rc = -ENAMETOOLONG;
@@ -588,6 +610,7 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
 		break;
 	}
 	__putname(path);
+	__putname(fw_path_string);
 
 	return rc;
 }
-- 
2.31.1