On Thu, 2008-05-01 at 08:47 -0700, Chris Wright wrote: > * Tetsuo Handa (penguin-kernel@xxxxxxxxxxxxxxxxxxx) wrote: > > The MAY_WRITE flag is not passed to security_inode_permission() > > if security_inode_permission() is called from __open_namei_create(). > > Since TOMOYO Linux doesn't check MAY_READ/MAY_WRITE permissions for individual > > read()/write() requests, the permission checks at open() time (i.e. may_open()) > > is the only chance to check MAY_WRITE flag. If I can't check MAY_WRITE flag > > here, TOMOYO Linux can't control open(O_WRONLY | O_CREATE | O_EXCL). > > > > Also, the O_TRUNC flag is not passed to security_inode_permission() because > > vfs_permission() receives only MAY_READ/MAY_WRITE/MAY_APPEND flags, but > > I have to check O_TRUNC flag before do_truncate(). > > > > So, I inserted a new hook here so that this hook can check all > > MAY_READ/MAY_WRITE/O_APPEND/O_TRUNC flags together in a single place. > > The reason I ask is because it doesn't check. It only checks O_APPEND, > but that's already passed in (MAY_APPEND). So AFAICT, it's only O_TRUNC > that you are trying to special case. But in that case...all that is > being asked for is MAY_WRITE permission. Anything else doesn't make > sense, especially since that's all you get from the truncate(2) path. > > <snip> > > This is an inevitable duplication since I want to do conventional checks > > (DAC checks and inode operation existence checks) before TOMOYO Linux's check. > > > > By the way, Stephen Smalley thinks it is better to copy codes which is needed by > > pre_vfs_*() (i.e. may_create()/may_delete()/check_sticky()) into > > security/tomoyo/ directory and leave vfs_*() untouched rather than > > extract pre_vfs_*() from vfs_*() and call pre_vfs_*() from vfs_*(). > > I'm not sure he means literally copy. Typically we take existing > functionality and make it externally usable. I didn't think splitting pre functions out of all of the vfs helpers was such a good idea. Making may_create/delete() available might make sense. And for complex combinations of DAC logic, perhaps introducing may_link(), may_rename(), etc. might make sense. > Also, all the changes you make that are not in vfs_* helpers won't get > picked up by NFS. -- Stephen Smalley National Security Agency -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
