f2fs: use generic checking function for FS_IOC_FSSETXATTR

Make the f2fs implementation of FS_IOC_FSSETXATTR use the new VFS helper
function vfs_ioc_fssetxattr_check(), and remove the project quota check
since it's now done by the helper function.

This is based on a patch from Darrick Wong, but reworked to apply after
commit 360985573b55 ("f2fs: separate f2fs i_flags from fs_flags and ext4
i_flags").

Originally-from: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/file.c

@@ -2862,52 +2862,32 @@ static inline u32 f2fs_xflags_to_iflags(u32 xflags)
 	return iflags;
 }
 
-static int f2fs_ioc_fsgetxattr(struct file *filp, unsigned long arg)
+static void f2fs_fill_fsxattr(struct inode *inode, struct fsxattr *fa)
 {
-	struct inode *inode = file_inode(filp);
 	struct f2fs_inode_info *fi = F2FS_I(inode);
-	struct fsxattr fa;
 
-	memset(&fa, 0, sizeof(struct fsxattr));
-	fa.fsx_xflags = f2fs_iflags_to_xflags(fi->i_flags);
+	simple_fill_fsxattr(fa, f2fs_iflags_to_xflags(fi->i_flags));
 
 	if (f2fs_sb_has_project_quota(F2FS_I_SB(inode)))
-		fa.fsx_projid = (__u32)from_kprojid(&init_user_ns,
-							fi->i_projid);
-
-	if (copy_to_user((struct fsxattr __user *)arg, &fa, sizeof(fa)))
-		return -EFAULT;
-	return 0;
+		fa->fsx_projid = from_kprojid(&init_user_ns, fi->i_projid);
 }
 
-static int f2fs_ioctl_check_project(struct inode *inode, struct fsxattr *fa)
+static int f2fs_ioc_fsgetxattr(struct file *filp, unsigned long arg)
 {
-	/*
-	 * Project Quota ID state is only allowed to change from within the init
-	 * namespace. Enforce that restriction only if we are trying to change
-	 * the quota ID state. Everything else is allowed in user namespaces.
-	 */
-	if (current_user_ns() == &init_user_ns)
-		return 0;
-
-	if (__kprojid_val(F2FS_I(inode)->i_projid) != fa->fsx_projid)
-		return -EINVAL;
+	struct inode *inode = file_inode(filp);
+	struct fsxattr fa;
 
-	if (F2FS_I(inode)->i_flags & F2FS_PROJINHERIT_FL) {
-		if (!(fa->fsx_xflags & FS_XFLAG_PROJINHERIT))
-			return -EINVAL;
-	} else {
-		if (fa->fsx_xflags & FS_XFLAG_PROJINHERIT)
-			return -EINVAL;
-	}
+	f2fs_fill_fsxattr(inode, &fa);
 
+	if (copy_to_user((struct fsxattr __user *)arg, &fa, sizeof(fa)))
+		return -EFAULT;
 	return 0;
 }
 
 static int f2fs_ioc_fssetxattr(struct file *filp, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
-	struct fsxattr fa;
+	struct fsxattr fa, old_fa;
 	u32 iflags;
 	int err;
 
@@ -2930,9 +2910,12 @@ static int f2fs_ioc_fssetxattr(struct file *filp, unsigned long arg)
 		return err;
 
 	inode_lock(inode);
-	err = f2fs_ioctl_check_project(inode, &fa);
+
+	f2fs_fill_fsxattr(inode, &old_fa);
+	err = vfs_ioc_fssetxattr_check(inode, &old_fa, &fa);
 	if (err)
 		goto out;
+
 	err = f2fs_setflags_common(inode, iflags,
 			f2fs_xflags_to_iflags(F2FS_SUPPORTED_XFLAGS));
 	if (err)

fs/inode.c

@@ -2149,3 +2149,65 @@ int vfs_ioc_setflags_prepare(struct inode *inode, unsigned int oldflags,
 	return 0;
 }
 EXPORT_SYMBOL(vfs_ioc_setflags_prepare);
+
+/*
+ * Generic function to check FS_IOC_FSSETXATTR values and reject any invalid
+ * configurations.
+ *
+ * Note: the caller should be holding i_mutex, or else be sure that they have
+ * exclusive access to the inode structure.
+ */
+int vfs_ioc_fssetxattr_check(struct inode *inode, const struct fsxattr *old_fa,
+			     struct fsxattr *fa)
+{
+	/*
+	 * Can't modify an immutable/append-only file unless we have
+	 * appropriate permission.
+	 */
+	if ((old_fa->fsx_xflags ^ fa->fsx_xflags) &
+			(FS_XFLAG_IMMUTABLE | FS_XFLAG_APPEND) &&
+	    !capable(CAP_LINUX_IMMUTABLE))
+		return -EPERM;
+
+	/*
+	 * Project Quota ID state is only allowed to change from within the init
+	 * namespace. Enforce that restriction only if we are trying to change
+	 * the quota ID state. Everything else is allowed in user namespaces.
+	 */
+	if (current_user_ns() != &init_user_ns) {
+		if (old_fa->fsx_projid != fa->fsx_projid)
+			return -EINVAL;
+		if ((old_fa->fsx_xflags ^ fa->fsx_xflags) &
+				FS_XFLAG_PROJINHERIT)
+			return -EINVAL;
+	}
+
+	/* Check extent size hints. */
+	if ((fa->fsx_xflags & FS_XFLAG_EXTSIZE) && !S_ISREG(inode->i_mode))
+		return -EINVAL;
+
+	if ((fa->fsx_xflags & FS_XFLAG_EXTSZINHERIT) &&
+			!S_ISDIR(inode->i_mode))
+		return -EINVAL;
+
+	if ((fa->fsx_xflags & FS_XFLAG_COWEXTSIZE) &&
+	    !S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
+		return -EINVAL;
+
+	/*
+	 * It is only valid to set the DAX flag on regular files and
+	 * directories on filesystems.
+	 */
+	if ((fa->fsx_xflags & FS_XFLAG_DAX) &&
+	    !(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)))
+		return -EINVAL;
+
+	/* Extent size hints of zero turn off the flags. */
+	if (fa->fsx_extsize == 0)
+		fa->fsx_xflags &= ~(FS_XFLAG_EXTSIZE | FS_XFLAG_EXTSZINHERIT);
+	if (fa->fsx_cowextsize == 0)
+		fa->fsx_xflags &= ~FS_XFLAG_COWEXTSIZE;
+
+	return 0;
+}
+EXPORT_SYMBOL(vfs_ioc_fssetxattr_check);

include/linux/fs.h

@@ -3397,4 +3397,13 @@ extern void inode_nohighmem(struct inode *inode);
 int vfs_ioc_setflags_prepare(struct inode *inode, unsigned int oldflags,
 			     unsigned int flags);
 
+int vfs_ioc_fssetxattr_check(struct inode *inode, const struct fsxattr *old_fa,
+			     struct fsxattr *fa);
+
+static inline void simple_fill_fsxattr(struct fsxattr *fa, __u32 xflags)
+{
+	memset(fa, 0, sizeof(*fa));
+	fa->fsx_xflags = xflags;
+}
+
 #endif /* _LINUX_FS_H */