ovl: use generic vfs_ioc_setflags_prepare() helper

Canonalize to ioctl FS_* flags instead of inode S_* flags.

Note that we do not call the helper vfs_ioc_fssetxattr_check()
for FS_IOC_FSSETXATTR ioctl. The reason is that underlying filesystem
will perform all the checks. We only need to perform the capability
check before overriding credentials.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 443986c..efccb7c 100644 (file)
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -559,12 +559,28 @@ static long ovl_real_ioctl(struct file *file, unsigned int cmd,
        return ret;
 }
 
+static unsigned int ovl_iflags_to_fsflags(unsigned int iflags)
+{
+       unsigned int flags = 0;
+
+       if (iflags & S_SYNC)
+               flags |= FS_SYNC_FL;
+       if (iflags & S_APPEND)
+               flags |= FS_APPEND_FL;
+       if (iflags & S_IMMUTABLE)
+               flags |= FS_IMMUTABLE_FL;
+       if (iflags & S_NOATIME)
+               flags |= FS_NOATIME_FL;
+
+       return flags;
+}
+
 static long ovl_ioctl_set_flags(struct file *file, unsigned int cmd,
-                               unsigned long arg, unsigned int iflags)
+                               unsigned long arg, unsigned int flags)
 {
        long ret;
        struct inode *inode = file_inode(file);
-       unsigned int old_iflags;
+       unsigned int oldflags;
 
        if (!inode_owner_or_capable(inode))
                return -EACCES;
@@ -576,10 +592,9 @@ static long ovl_ioctl_set_flags(struct file *file, unsigned int cmd,
        inode_lock(inode);
 
        /* Check the capability before cred override */
-       ret = -EPERM;
-       old_iflags = READ_ONCE(inode->i_flags);
-       if (((iflags ^ old_iflags) & (S_APPEND | S_IMMUTABLE)) &&
-           !capable(CAP_LINUX_IMMUTABLE))
+       oldflags = ovl_iflags_to_fsflags(READ_ONCE(inode->i_flags));
+       ret = vfs_ioc_setflags_prepare(inode, oldflags, flags);
+       if (ret)
                goto unlock;
 
        ret = ovl_maybe_copy_up(file_dentry(file), O_WRONLY);
@@ -598,22 +613,6 @@ unlock:
 
 }
 
-static unsigned int ovl_fsflags_to_iflags(unsigned int flags)
-{
-       unsigned int iflags = 0;
-
-       if (flags & FS_SYNC_FL)
-               iflags |= S_SYNC;
-       if (flags & FS_APPEND_FL)
-               iflags |= S_APPEND;
-       if (flags & FS_IMMUTABLE_FL)
-               iflags |= S_IMMUTABLE;
-       if (flags & FS_NOATIME_FL)
-               iflags |= S_NOATIME;
-
-       return iflags;
-}
-
 static long ovl_ioctl_set_fsflags(struct file *file, unsigned int cmd,
                                  unsigned long arg)
 {
@@ -622,24 +621,23 @@ static long ovl_ioctl_set_fsflags(struct file *file, unsigned int cmd,
        if (get_user(flags, (int __user *) arg))
                return -EFAULT;
 
-       return ovl_ioctl_set_flags(file, cmd, arg,
-                                  ovl_fsflags_to_iflags(flags));
+       return ovl_ioctl_set_flags(file, cmd, arg, flags);
 }
 
-static unsigned int ovl_fsxflags_to_iflags(unsigned int xflags)
+static unsigned int ovl_fsxflags_to_fsflags(unsigned int xflags)
 {
-       unsigned int iflags = 0;
+       unsigned int flags = 0;
 
        if (xflags & FS_XFLAG_SYNC)
-               iflags |= S_SYNC;
+               flags |= FS_SYNC_FL;
        if (xflags & FS_XFLAG_APPEND)
-               iflags |= S_APPEND;
+               flags |= FS_APPEND_FL;
        if (xflags & FS_XFLAG_IMMUTABLE)
-               iflags |= S_IMMUTABLE;
+               flags |= FS_IMMUTABLE_FL;
        if (xflags & FS_XFLAG_NOATIME)
-               iflags |= S_NOATIME;
+               flags |= FS_NOATIME_FL;
 
-       return iflags;
+       return flags;
 }
 
 static long ovl_ioctl_set_fsxflags(struct file *file, unsigned int cmd,
@@ -652,7 +650,7 @@ static long ovl_ioctl_set_fsxflags(struct file *file, unsigned int cmd,
                return -EFAULT;
 
        return ovl_ioctl_set_flags(file, cmd, arg,
-                                  ovl_fsxflags_to_iflags(fa.fsx_xflags));
+                                  ovl_fsxflags_to_fsflags(fa.fsx_xflags));
 }
 
 long ovl_ioctl(struct file *file, unsigned int cmd, unsigned long arg)