linux-kernel - [PATCH] firmware_loader: Strip off \n from customized path

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Date:   Thu, 13 Apr 2023 12:17:57 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     corbet@....net, Florian Fainelli <f.fainelli@...il.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Russ Weight <russell.h.weight@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: [PATCH] firmware_loader: Strip off \n from customized path

Having helped an user recently figure out why the customized path being
specified was not taken into account landed on a subtle difference
between using:

echo "/xyz/firmware" > /sys/module/firmware_class/parameters/path

which inserts an additional newline which is passed as is down to
fw_get_filesystem_firmware() and ultimately kernel_read_file_from_path()
and fails.

Strip off \n from the customized firmware path such that users do not
run into these hard to debug situations.

Link: https://lore.kernel.org/all/20230402135423.3235-1-f.fainelli@gmail.com/
Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
---
 drivers/base/firmware_loader/main.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index 017c4cdb219e..10b7d8fc5d07 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -493,9 +493,9 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
 					     const void *in_buffer))
 {
 	size_t size;
-	int i, len;
+	int i, len, maxlen = 0;
 	int rc = -ENOENT;
-	char *path;
+	char *path, *nt = NULL;
 	size_t msize = INT_MAX;
 	void *buffer = NULL;
 
@@ -518,8 +518,17 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
 		if (!fw_path[i][0])
 			continue;
 
-		len = snprintf(path, PATH_MAX, "%s/%s%s",
-			       fw_path[i], fw_priv->fw_name, suffix);
+		/* strip off \n from customized path */
+		maxlen = strlen(fw_path[i]);
+		if (i == 0) {
+			nt = strchr(fw_path[i], '\n');
+			if (nt)
+				maxlen = nt - fw_path[i];
+		}
+
+		len = snprintf(path, PATH_MAX, "%.*s/%s%s",
+			       maxlen, fw_path[i],
+			       fw_priv->fw_name, suffix);
 		if (len >= PATH_MAX) {
 			rc = -ENAMETOOLONG;
 			break;
-- 
2.34.1