On Tue 13-06-23 14:01:03, Theodore Ts'o wrote: > I wonder if we should have a separate syzkaller subsystem for ext2 (as > distinct from ext4)? The syz reproducer seems to know that it should > be mounting using ext2, but also calls it an ext4 file system, which > is a bit weird. I'm guessing there is something specific about the > syzkaller internals which might not make this be practical, but I > thought I should ask. Yeah, having ext2 driver as a separate subsystem makes sense to me since it is completely different codebase. > From the syz reproducer: > > syz_mount_image$ext4(&(0x7f0000000100)='ext2\x00', ...) > > More generally, there are a series of changes that were made to make > ext4 to make it more robust against maliciously fuzzed superblocks, > but we haven't necessarily made sure the same analogous changes have > been made to ext2. I'm not sure how critical this is in practice, > since most distributions don't actually compile fs/ext2 and instead > use CONFIG_EXT4_USE_FOR_EXT2 instead. However, while we maintain ext2 > as a sample "simple" modern file system, I guess we should try to make > sure we do carry those fixes over. > > Jan, as the ext2 maintainer, do you have an opinion? I agree, I try to fix these problems when syzbot finds them. For this one, I've already sent a fix [1] (dropping remains of fragments support from ext2). Honza [1] https://lore.kernel.org/all/20230613103012.22933-1-jack@xxxxxxx -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
