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15baf55481
Master keys can be in one of three states: present, incompletely removed, and absent (as per FSCRYPT_KEY_STATUS_* used in the UAPI). Currently, the way that "present" is distinguished from "incompletely removed" internally is by whether ->mk_secret exists or not. With extent-based encryption, it will be necessary to allow per-extent keys to be derived while the master key is incompletely removed, so that I/O on open files will reliably continue working after removal of the key has been initiated. (We could allow I/O to sometimes fail in that case, but that seems problematic for reasons such as writes getting silently thrown away and diverging from the existing fscrypt semantics.) Therefore, when the filesystem is using extent-based encryption, ->mk_secret can't be wiped when the key becomes incompletely removed. As a prerequisite for doing that, this patch makes the "present" state be tracked using a new field, ->mk_present. No behavior is changed yet. The basic idea here is borrowed from Josef Bacik's patch "fscrypt: use a flag to indicate that the master key is being evicted" (https://lore.kernel.org/r/e86c16dddc049ff065f877d793ad773e4c6bfad9.1696970227.git.josef@toxicpanda.com). I reimplemented it using a "present" bool instead of an "evicted" flag, fixed a couple bugs, and tried to update everything to be consistent. Note: I considered adding a ->mk_status field instead, holding one of FSCRYPT_KEY_STATUS_*. At first that seemed nice, but it ended up being more complex (despite simplifying FS_IOC_GET_ENCRYPTION_KEY_STATUS), since it would have introduced redundancy and had weird locking rules. Reviewed-by: Neal Gompa <neal@gompa.dev> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Link: https://lore.kernel.org/r/20231015061055.62673-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com> |
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