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Date: Thu, 25 Mar 2021 20:37:40 +0100
From: Miklos Szeredi <mszeredi@...hat.com>
To: linux-fsdevel@...r.kernel.org
Cc: Al Viro <viro@...IV.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: [PATCH v3 03/18] ovl: stack fileattr ops
Add stacking for the fileattr operations.
Add hack for calling security_file_ioctl() for now. Probably better to
have a pair of specific hooks for these operations.
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
---
fs/overlayfs/dir.c | 2 ++
fs/overlayfs/inode.c | 77 ++++++++++++++++++++++++++++++++++++++++
fs/overlayfs/overlayfs.h | 3 ++
3 files changed, 82 insertions(+)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 836f14b9d3a6..93efe7048a77 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -1301,4 +1301,6 @@ const struct inode_operations ovl_dir_inode_operations = {
.listxattr = ovl_listxattr,
.get_acl = ovl_get_acl,
.update_time = ovl_update_time,
+ .fileattr_get = ovl_fileattr_get,
+ .fileattr_set = ovl_fileattr_set,
};
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 003cf83bf78a..c3c96b4b3b33 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -11,6 +11,8 @@
#include <linux/posix_acl.h>
#include <linux/ratelimit.h>
#include <linux/fiemap.h>
+#include <linux/fileattr.h>
+#include <linux/security.h>
#include "overlayfs.h"
@@ -500,6 +502,79 @@ static int ovl_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
return err;
}
+/*
+ * Work around the fact that security_file_ioctl() takes a file argument.
+ * Introducing security_inode_fileattr_get/set() hooks would solve this issue
+ * properly.
+ */
+static int ovl_security_fileattr(struct dentry *dentry, struct fileattr *fa,
+ bool set)
+{
+ struct path realpath;
+ struct file *file;
+ unsigned int cmd;
+ int err;
+
+ ovl_path_real(dentry, &realpath);
+ file = dentry_open(&realpath, O_RDONLY, current_cred());
+ if (IS_ERR(file))
+ return PTR_ERR(file);
+
+ if (set)
+ cmd = fa->fsx_valid ? FS_IOC_FSSETXATTR : FS_IOC_SETFLAGS;
+ else
+ cmd = fa->fsx_valid ? FS_IOC_FSGETXATTR : FS_IOC_GETFLAGS;
+
+ err = security_file_ioctl(file, cmd, 0);
+ fput(file);
+
+ return err;
+}
+
+int ovl_fileattr_set(struct user_namespace *mnt_userns,
+ struct dentry *dentry, struct fileattr *fa)
+{
+ struct inode *inode = d_inode(dentry);
+ struct dentry *upperdentry;
+ const struct cred *old_cred;
+ int err;
+
+ err = ovl_want_write(dentry);
+ if (err)
+ goto out;
+
+ err = ovl_copy_up(dentry);
+ if (!err) {
+ upperdentry = ovl_dentry_upper(dentry);
+
+ old_cred = ovl_override_creds(inode->i_sb);
+ err = ovl_security_fileattr(dentry, fa, true);
+ if (!err)
+ err = vfs_fileattr_set(&init_user_ns, upperdentry, fa);
+ revert_creds(old_cred);
+ ovl_copyflags(ovl_inode_real(inode), inode);
+ }
+ ovl_drop_write(dentry);
+out:
+ return err;
+}
+
+int ovl_fileattr_get(struct dentry *dentry, struct fileattr *fa)
+{
+ struct inode *inode = d_inode(dentry);
+ struct dentry *realdentry = ovl_dentry_real(dentry);
+ const struct cred *old_cred;
+ int err;
+
+ old_cred = ovl_override_creds(inode->i_sb);
+ err = ovl_security_fileattr(dentry, fa, false);
+ if (!err)
+ err = vfs_fileattr_get(realdentry, fa);
+ revert_creds(old_cred);
+
+ return err;
+}
+
static const struct inode_operations ovl_file_inode_operations = {
.setattr = ovl_setattr,
.permission = ovl_permission,
@@ -508,6 +583,8 @@ static const struct inode_operations ovl_file_inode_operations = {
.get_acl = ovl_get_acl,
.update_time = ovl_update_time,
.fiemap = ovl_fiemap,
+ .fileattr_get = ovl_fileattr_get,
+ .fileattr_set = ovl_fileattr_set,
};
static const struct inode_operations ovl_symlink_inode_operations = {
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 95cff83786a5..a1c1b5ae59e9 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -521,6 +521,9 @@ int __init ovl_aio_request_cache_init(void);
void ovl_aio_request_cache_destroy(void);
long ovl_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
long ovl_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
+int ovl_fileattr_get(struct dentry *dentry, struct fileattr *fa);
+int ovl_fileattr_set(struct user_namespace *mnt_userns,
+ struct dentry *dentry, struct fileattr *fa);
/* copy_up.c */
int ovl_copy_up(struct dentry *dentry);
--
2.30.2
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