[PATCH 3/6] ext4: don't inherit inappropriate inode flags from parent - Kernel

At present INDEX and EXTENTS are the only flags that new ext4 inodes do
NOT inherit from their parent. In addition prevent the flags DIRTY, ECOMPR,
IMAGIC, TOPDIR, HUGE_FILE and EXT_MIGRATE from being inherited. List
inheritable flags explicitly to prevent future flags from accidentally being
inherited.

Signed-off-by: Duane Griffin
--

This is v2 with inheritable flags now explicitly specified, as per Andreas'
request.

---
fs/ext4/ext4.h | 8 ++++++++
fs/ext4/ialloc.c | 2 +-
2 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 8158083..1a4faa5 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -235,6 +235,14 @@ struct ext4_group_desc
#define EXT4_FL_USER_VISIBLE 0x000BDFFF /* User visible flags */
#define EXT4_FL_USER_MODIFIABLE 0x000380FF /* User modifiable flags */

+/* Flags that should be inherited by new inodes from their parent. */
+#define EXT4_FL_INHERITED (EXT4_SECRM_FL | EXT4_UNRM_FL | EXT4_COMPR_FL |\
+ EXT4_SYNC_FL | EXT4_IMMUTABLE_FL | EXT4_APPEND_FL |\
+ EXT4_NODUMP_FL | EXT4_NOATIME_FL |\
+ EXT4_COMPRBLK_FL | EXT4_NOCOMPR_FL |\
+ EXT4_JOURNAL_DATA_FL | EXT4_NOTAIL_FL|\
+ EXT4_DIRSYNC_FL)
+
/*
* Inode dynamic state flags
*/
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index c6efbab..ff25d57 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -702,7 +702,7 @@ got:
* newly created directory and file only if -o extent mount option is
* specified
*/
- ei->i_flags = EXT4_I(dir)->i_flags & ~(EXT4_INDEX_FL|EXT4_EXTENTS_FL);
+ ei->i_flags = EXT4_I(dir)->i_flags & EXT4_FL_INHERITED;
if (S_ISLNK(mode))
ei->i_flags &= ~(EXT4_IMMUTABLE_FL|EXT4_APPEND_FL);
/* dirsync only applies to directories */
--
1.5.3.7

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At the moment there are few restrictions on which flags may be set on which
inodes. Specifically DIRSYNC may only be set on directories and IMMUTABLE
and APPEND may not be set on links. Tighten that to disallow TOPDIR being
set on non-directories and SECRM, UNRM, COMPR, SYNC, DIRTY, COMPRBLK,
NOCOMP, ECOMPR, INDEX, JOURNAL_DATA and NOTAIL being set on anything but
regular files or directories.

Introduce a flags masking function which masks flags based on mode and use
it during inode creation and when flags are set via the ioctl to facilitate
future consistency.

Signed-off-by: Duane Griffin
--

The specific flags masked out here are those suggested by Andreas, as well
as IMMUTABLE, which I included to match the behaviour of the existing code.

It would be good to get some review of these.

---
fs/ext2/ialloc.c | 8 ++------
fs/ext2/ioctl.c | 3 +--
include/linux/ext2_fs.h | 22 ++++++++++++++++++++++
3 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/fs/ext2/ialloc.c b/fs/ext2/ialloc.c
index a51d4ca..1559b8e 100644
--- a/fs/ext2/ialloc.c
+++ b/fs/ext2/ialloc.c
@@ -565,12 +565,8 @@ got:
inode->i_blocks = 0;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME_SEC;
memset(ei->i_data, 0, sizeof(ei->i_data));
- ei->i_flags = EXT2_I(dir)->i_flags & EXT2_FL_INHERITED;
- if (S_ISLNK(mode))
- ei->i_flags &= ~(EXT2_IMMUTABLE_FL|EXT2_APPEND_FL);
- /* dirsync is only applied to directories */
- if (!S_ISDIR(mode))
- ei->i_flags &= ~EXT2_DIRSYNC_FL;
+ ei->i_flags =
+ ext2_mask_flags(mode, EXT2_I(dir)->i_flags & EXT2_FL_INHERITED);
ei->i_faddr = 0;
ei->i_frag_no = 0;
ei->i_frag_size = 0;
diff --git a/fs/ext2/ioctl.c b/fs/ext2/ioctl.c
index de876fa..7cb4bad 100644
--- a/fs/ext2/ioctl.c
+++ b/fs/ext2/ioctl.c
@@ -50,8 +50,7 @@ long ext2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
goto setflags_out;
}

- if (!S_ISDIR(inode->i_mode))
- flags &= ~EXT2_DIRSYNC_FL;
+ flags = ext2_mask_flags(inode->i_mode, flags);

mutex_lock(&inode->i_mutex);
/* Is it quota file? Do not allow user to mess with it */
diff --git a/include/linux/ext2_fs.h b/include/linux/ext2_fs.h
index 7ead7eb..48a6cc1 100644
--- a/include/linux/ext2_fs.h
+++ b/include/linux/ext2_fs.h
@@ -201,6 +201,28 @@ struct ext2_group_desc
EXT2_NOCOMP_FL | EXT2_JOURNAL_DATA_FL |\
EXT2_NOTAIL_FL | EXT2_DIRSYNC_FL)

+/* Flags that are inappropriate for regular files. */
+#define EXT2_REG_FLMASK (EXT2_DIRSYNC_FL | EXT2_TOPDIR_FL)
+
+/* Flags that are inappropriate for non-directories/regular files. */
+#define EXT2_OTHER_FLMASK (EXT2_SECRM_FL | EXT2_UNRM_FL | EXT2_COMPR_FL |\
+ EXT2_SYNC_FL | EXT2_IMMUTABLE_FL | EXT2_APPEND_FL |\
+ EXT2_DIRTY_FL | EXT2_COMPRBLK_FL | EXT2_NOCOMP_FL |\
+ EXT2_ECOMPR_FL | EXT2_INDEX_FL |\
+ EXT2_JOURNAL_DATA_FL | EXT2_NOTAIL_FL |\
+ EXT2_DIRSYNC_FL | EXT2_TOPDIR_FL)
+
+/* Mask out flags that are inappropriate for the given type of inode. */
+static inline __le32 ext2_mask_flags(__le16 mode, __le32 flags)
+{
+ if (S_ISDIR(mode))
+ return flags;
+ else if (S_ISREG(mode))
+ return flags & ~EXT2_REG_FLMASK;
+ else
+ return flags & ~EXT2_OTHER_FLMASK;
+}
+
/*
* ioctl commands
*/
--
1.5.3.7

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