[PATCH] fix umask when noACL kernel meets extN tuned for ACLs

Fix insecure default behaviour reported by Tigran Aivazian: if an ext2 or
ext3 or ext4 filesystem is tuned to mount with "acl", but mounted by a
kernel built without ACL support, then umask was ignored when creating
inodes - though root or user has umask 022, touch creates files as 0666,
and mkdir creates directories as 0777.

This appears to have worked right until 2.6.11, when a fix to the default
mode on symlinks (always 0777) assumed VFS applies umask: which it does,
unless the mount is marked for ACLs; but ext[234] set MS_POSIXACL in
s_flags according to s_mount_opt set according to def_mount_opts.

We could revert to the 2.6.10 ext[234]_init_acl (adding an S_ISLNK test);
but other filesystems only set MS_POSIXACL when ACLs are configured.  We
could fix this at another level; but it seems most robust to avoid setting
the s_mount_opt flag in the first place (at the expense of more ifdefs).

Likewise don't set the XATTR_USER flag when built without XATTR support.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Tigran Aivazian <tigran@aivazian.fsnet.co.uk>
Cc: <linux-ext4@vger.kernel.org>
Cc: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 463b52b32a0e..c63a18b574dd 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1518,10 +1518,14 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
                 set_opt(sbi->s_mount_opt, GRPID);
         if (def_mount_opts & EXT4_DEFM_UID16)
                 set_opt(sbi->s_mount_opt, NO_UID32);
+#ifdef CONFIG_EXT4DEV_FS_XATTR
         if (def_mount_opts & EXT4_DEFM_XATTR_USER)
                 set_opt(sbi->s_mount_opt, XATTR_USER);
+#endif
+#ifdef CONFIG_EXT4DEV_FS_POSIX_ACL
         if (def_mount_opts & EXT4_DEFM_ACL)
                 set_opt(sbi->s_mount_opt, POSIX_ACL);
+#endif
         if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_DATA)
                 sbi->s_mount_opt |= EXT4_MOUNT_JOURNAL_DATA;
         else if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_ORDERED)