On Tue, Jun 23, 2020 at 10:57 PM Eric Biggers <ebiggers@xxxxxxxxxx> wrote: > > Note that the '!IS_ENCRYPTED(dir) || fscrypt_has_encryption_key(dir)' check can > be racy, because a process can be looking up a no-key token in a directory while > concurrently another process initializes the directory's ->i_crypt_info, causing > fscrypt_has_encryption_key(dir) to suddenly start returning true. > > In my rework of filename handling in f2fs, I actually ended up removing all > calls to needs_casefold(), thus avoiding this race. f2fs now decides whether > the name is going to need casefolding early on, in __f2fs_setup_filename(), > where it knows in a race-free way whether the filename is a no-key token or not. > > Perhaps ext4 should work the same way? It did look like there would be some > extra complexity due to how the ext4 directory hashing works in comparison to > f2fs's, but I haven't had a chance to properly investigate it. > > - Eric Hm. I think I should be able to just check for DCACHE_ENCRYPTED_NAME in the dentry here, right? I'm just trying to avoid casefolding the no-key token, and that flag should indicate that. I'll see if I can rework the ext4 patches to not need needs_casefold as well, since then there'd be no need to export it. -Daniel
