From: Nicolai Stange Date: Tue, 24 May 2016 11:08:53 +0000 (+0200) Subject: debugfs: full_proxy_open(): free proxy on ->open() failure X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=b10e3e90485e32e4cea9e35d2295ee7bffaeff73;p=openwrt%2Fstaging%2Fblogic.git debugfs: full_proxy_open(): free proxy on ->open() failure Debugfs' full_proxy_open(), the ->open() installed at all inodes created through debugfs_create_file(), - grabs a reference to the original struct file_operations instance passed to debugfs_create_file(), - dynamically allocates a proxy struct file_operations instance wrapping the original - and installs this at the file's ->f_op. Afterwards, it calls the original ->open() and passes its return value back to the VFS layer. Now, if that return value indicates failure, the VFS layer won't ever call ->release() and thus, neither the reference to the original file_operations nor the memory for the proxy file_operations will get released, i.e. both are leaked. Upon failure of the original fops' ->open(), undo the proxy installation. That is: - Set the struct file ->f_op to what it had been when full_proxy_open() was entered. - Drop the reference to the original file_operations. - Free the memory holding the proxy file_operations. Fixes: 49d200deaa68 ("debugfs: prevent access to removed files' private data") Signed-off-by: Nicolai Stange Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c index 9c1c9a01b7e5..d1ec80331414 100644 --- a/fs/debugfs/file.c +++ b/fs/debugfs/file.c @@ -262,8 +262,10 @@ static int full_proxy_open(struct inode *inode, struct file *filp) if (real_fops->open) { r = real_fops->open(inode, filp); - - if (filp->f_op != proxy_fops) { + if (r) { + replace_fops(filp, d_inode(dentry)->i_fop); + goto free_proxy; + } else if (filp->f_op != proxy_fops) { /* No protection against file removal anymore. */ WARN(1, "debugfs file owner replaced proxy fops: %pd", dentry);