On Mon 11-06-12 15:01:08, Ted Tso wrote: > On Mon, Jun 11, 2012 at 06:41:30PM +0300, Boaz Harrosh wrote: > > > > My point being that please any changes made to ext2, in this area please also > > apply to exofs, since it is just another copy/paste of ext2. I'll ACK any > > which way you guys decide to properly go with, as part of the VFS changes. > > Well, I already have this quick and dirty fix to address the problem > in ext4. See commit 7e936b7372. If we need to make changes to all of > the file systems to accomodate some new VFS abstraction, it might be > worth considering whether it's easier/simpler to just put in a quick > check like I did for ext4 (just so I could plug the security hole[1] > quickly). > > [1] It's a denial of service attack for kiosks that do automounts of > USB sticks; granted, it's not that big a of a security deal, but some > people care about such things. > > Of course, if the new/changed VFS abstraction solves other problems, > that's cool, but if not, sometimes a simple brute force check is > better than something complicated if elegant. :-) I think that fix in ext4 is fine. Just you don't catch the situation when the directory entry points e.g. to a parent and that's deadlockable trivially as well. Even if it points to some unrelated directory, you can easily deadlock rename which tries to lock both directories. So I attempted for a fix in VFS because that's the only place having enough information to be able to tell whether you are creating directory hardlink or not. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
