linux-kernel - [PATCH v5 7/8] debugfs: unproxify files created through debugfs_create

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1457267103-28910-8-git-send-email-nicstange@gmail.com>
Date:	Sun,  6 Mar 2016 13:25:02 +0100
From:	Nicolai Stange <nicstange@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jonathan Corbet <corbet@....net>, Jan Kara <jack@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Julia Lawall <Julia.Lawall@...6.fr>,
	Gilles Muller <Gilles.Muller@...6.fr>,
	Nicolas Palix <nicolas.palix@...g.fr>,
	Michal Marek <mmarek@...e.com>, linux-kernel@...r.kernel.org,
	cocci@...teme.lip6.fr, Nicolai Stange <nicstange@...il.com>
Subject: [PATCH v5 7/8] debugfs: unproxify files created through debugfs_create_blob()

Currently, the struct file_operations fops_blob associated with files
created through the debugfs_create_blob() helpers are not file
lifetime aware.

Thus, a lifetime managing proxy is created around fops_blob each time such
a file is opened which is an unnecessary waste of resources.

Implement file lifetime management for the fops_bool file_operations.
Namely, make read_file_blob() safe gainst file removals by means of
debugfs_use_file_start() and debugfs_use_file_finish().

Make debugfs_create_blob() create its files in non-proxying operation mode
by means of debugfs_create_file_unsafe().

Signed-off-by: Nicolai Stange <nicstange@...il.com>
---
 fs/debugfs/file.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 4eac1a1..9d4bcd6 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -843,8 +843,15 @@ static ssize_t read_file_blob(struct file *file, char __user *user_buf,
 			      size_t count, loff_t *ppos)
 {
 	struct debugfs_blob_wrapper *blob = file->private_data;
-	return simple_read_from_buffer(user_buf, count, ppos, blob->data,
-			blob->size);
+	ssize_t r;
+	int srcu_idx;
+
+	r = debugfs_use_file_start(F_DENTRY(file), &srcu_idx);
+	if (likely(!r))
+		r = simple_read_from_buffer(user_buf, count, ppos, blob->data,
+					blob->size);
+	debugfs_use_file_finish(srcu_idx);
+	return r;
 }
 
 static const struct file_operations fops_blob = {
@@ -881,7 +888,7 @@ struct dentry *debugfs_create_blob(const char *name, umode_t mode,
 				   struct dentry *parent,
 				   struct debugfs_blob_wrapper *blob)
 {
-	return debugfs_create_file(name, mode, parent, blob, &fops_blob);
+	return debugfs_create_file_unsafe(name, mode, parent, blob, &fops_blob);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_blob);
 
-- 
2.7.2