On Wed, May 24, 2023 at 08:16:58AM +1000, Dave Chinner wrote: > config XFS_SUPPORT_V4 > bool "Support deprecated V4 (crc=0) format" > depends on XFS_FS > default y > help > The V4 filesystem format lacks certain features that are supported > by the V5 format, such as metadata checksumming, strengthened > metadata verification, and the ability to store timestamps past the > year 2038. Because of this, the V4 format is deprecated. All users > should upgrade by backing up their files, reformatting, and restoring > from the backup. > > Administrators and users can detect a V4 filesystem by running > xfs_info against a filesystem mountpoint and checking for a string > beginning with "crc=". If the string "crc=0" is found, the > filesystem is a V4 filesystem. If no such string is found, please > upgrade xfsprogs to the latest version and try again. > > This option will become default N in September 2025. Support for the > V4 format will be removed entirely in September 2030. Distributors > can say N here to withdraw support earlier. > > To continue supporting the old V4 format (crc=0), say Y. > To close off an attack surface, say N. > > This was added almost 3 years ago in mid-2020. We're more than half > way through the deprecation period and then we're going to turn off > v4 support by default. At this point, nobody should be using v4 > filesystems in new production systems, and those that are should be > preparing for upstream and distro support to be withdraw in the next > couple of years... Great to see that this exists now and there is a specific deprecation plan! > > Then you could just tell the people fuzzing XFS filesystem images > > that they need to use that option. That would save everyone a lot of time. > > (To be clear, I'm not arguing for the XFS policy on v4 filesystems being right > > or wrong; that's really not something I'd like to get into again... I'm just > > saying that if that's indeed your policy, this is what you should do.) > > It should be obvious by now that we've already done this. 3 years > ago, in fact. And yet we are still having the same problems. Maybe > this helps you understand the level of frustration we have with all > the people running fuzzing bots out there.... I don't see evidence that this actually happened, though perhaps we are not looking in the same places. https://lore.kernel.org/all/?q=XFS_SUPPORT_V4 brings up little except the original patch thread, nor did https://github.com/search?q=XFS_SUPPORT_V4&type=issues find anything. Anyway, I took 3 minutes to file an issue in the syzkaller repo (https://github.com/google/syzkaller/issues/3918), so at least this should get resolved for syzbot soon. - Eric
