linux-kernel - [PATCH] debugfs: only accept read attributes for blobs

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Message-Id: <20210504121721.43385-1-wsa+renesas@sang-engineering.com>
Date:   Tue,  4 May 2021 14:17:20 +0200
From:   Wolfram Sang <wsa+renesas@...g-engineering.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-renesas-soc@...r.kernel.org,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: [PATCH] debugfs: only accept read attributes for blobs

Blobs can only be read. So, keep only 'read' file attributes because the
others will not work and only confuse users.

Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
---

I was confused for a second, thinking blobs can be written to. I will
fix the few in-kernel users doing it wrong seperately.

 fs/debugfs/file.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 686e0ad28788..d6aa6e04b7af 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -890,7 +890,8 @@ static const struct file_operations fops_blob = {
 /**
  * debugfs_create_blob - create a debugfs file that is used to read a binary blob
  * @name: a pointer to a string containing the name of the file to create.
- * @mode: the permission that the file should have
+ * @mode: the read permission that the file should have (other permissions are
+ * 	  masked out)
  * @parent: a pointer to the parent dentry for this file.  This should be a
  *          directory dentry if set.  If this parameter is %NULL, then the
  *          file will be created in the root of the debugfs filesystem.
@@ -914,7 +915,7 @@ struct dentry *debugfs_create_blob(const char *name, umode_t mode,
 				   struct dentry *parent,
 				   struct debugfs_blob_wrapper *blob)
 {
-	return debugfs_create_file_unsafe(name, mode, parent, blob, &fops_blob);
+	return debugfs_create_file_unsafe(name, mode & S_IRUGO, parent, blob, &fops_blob);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_blob);
 
-- 
2.30.0