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authorLouis Rilling <louis.rilling@kerlabs.com>2008-07-04 16:56:05 +0200
committerMark Fasheh <mfasheh@suse.com>2008-07-31 16:21:13 -0700
commit2a109f2a4155f168047aa2f5b3a170e279bef89a (patch)
tree8e9a080046fb1abdba10e288b89e92cc4c39f6ea /fs/splice.c
parent9a73d78cda750f12e25eb811878f2d9dbab1bc6e (diff)
[PATCH] configfs: Prevent userspace from creating new entries under attaching directories
process 1: process 2: configfs_mkdir("A") attach_group("A") attach_item("A") d_instantiate("A") populate_groups("A") mutex_lock("A") attach_group("A/B") attach_item("A") d_instantiate("A/B") mkdir("A/B/C") do_path_lookup("A/B/C", LOOKUP_PARENT) ok lookup_create("A/B/C") mutex_lock("A/B") ok configfs_mkdir("A/B/C") ok attach_group("A/C") attach_item("A/C") d_instantiate("A/C") populate_groups("A/C") mutex_lock("A/C") attach_group("A/C/D") attach_item("A/C/D") failure mutex_unlock("A/C") detach_groups("A/C") nothing to do mkdir("A/C/E") do_path_lookup("A/C/E", LOOKUP_PARENT) ok lookup_create("A/C/E") mutex_lock("A/C") ok configfs_mkdir("A/C/E") ok detach_item("A/C") d_delete("A/C") mutex_unlock("A") detach_groups("A") mutex_lock("A/B") detach_group("A/B") detach_groups("A/B") nothing since no _default_ group detach_item("A/B") mutex_unlock("A/B") d_delete("A/B") detach_item("A") d_delete("A") Two bugs: 1/ "A/B/C" and "A/C/E" are created, but never removed while their parent are removed in the end. The same could happen with symlink() instead of mkdir(). 2/ "A" and "A/C" inodes are not locked while detach_item() is called on them, which may probably confuse VFS. This commit fixes 1/, tagging new directories with CONFIGFS_USET_CREATING before building the inode and instantiating the dentry, and validating the whole group+default groups hierarchy in a second pass by clearing CONFIGFS_USET_CREATING. mkdir(), symlink(), lookup(), and dir_open() simply return -ENOENT if called in (or linking to) a directory tagged with CONFIGFS_USET_CREATING. This does not prevent userspace from calling stat() successfuly on such directories, but this prevents userspace from adding (children to | symlinking from/to | read/write attributes of | listing the contents of) not validated items. In other words, userspace will not interact with the subsystem on a new item until the new item creation completes correctly. It was first proposed to re-use CONFIGFS_USET_IN_MKDIR instead of a new flag CONFIGFS_USET_CREATING, but this generated conflicts when checking the target of a new symlink: a valid target directory in the middle of attaching a new user-created child item could be wrongly detected as being attached. 2/ is fixed by next commit. Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Diffstat (limited to 'fs/splice.c')
0 files changed, 0 insertions, 0 deletions