linux-kernel - [PATCH v2] debugfs: fix refcount imbalance in start

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>] [day] [month] [year] [list]

Message-Id: <1d40118f3f42ca1e907cd7d4a254e53f4daa639d.1446672826.git.daniel@iogearbox.net>
Date:	Thu,  5 Nov 2015 00:01:51 +0100
From:	Daniel Borkmann <daniel@...earbox.net>
To:	gregkh@...uxfoundation.org
Cc:	rostedt@...dmis.org, viro@...IV.linux.org.uk,
	linux-kernel@...r.kernel.org,
	Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH v2] debugfs: fix refcount imbalance in start_creating

In debugfs' start_creating(), we pin the file system to safely access
its root. When we failed to create a file, we unpin the file system via
failed_creating() to release the mount count and eventually the reference
of the vfsmount.

However, when we run into an error during lookup_one_len() when still
in start_creating(), we only release the parent's mutex but not so the
reference on the mount. Looks like it was done in the past, but after
splitting portions of __create_file() into start_creating() and
end_creating() via 190afd81e4a5 ("debugfs: split the beginning and the
end of __create_file() off"), this seemed missed. Noticed during code
review.

Fixes: 190afd81e4a5 ("debugfs: split the beginning and the end of __create_file() off")
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
---
 v1 -> v2:
 - Split original patch into two patches (tracefs and debugfs)

 fs/debugfs/inode.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index c711be8..9c8d233 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -271,8 +271,12 @@ static struct dentry *start_creating(const char *name, struct dentry *parent)
 		dput(dentry);
 		dentry = ERR_PTR(-EEXIST);
 	}
-	if (IS_ERR(dentry))
+
+	if (IS_ERR(dentry)) {
 		mutex_unlock(&d_inode(parent)->i_mutex);
+		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
+	}
+
 	return dentry;
 }

-- 
1.9.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/