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fscrypt: improve fscrypt_destroy_keyring() documentation

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Document that fscrypt_destroy_keyring() must be called after all
potentially-encrypted inodes have been evicted.

Link: https://lore.kernel.org/r/20230313221231.272498-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers 2023-03-13 15:12:30 -07:00
parent ccb820dc7d
commit 43e5f1d592
1 changed files with 11 additions and 10 deletions
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21
fs/crypto/keyring.c
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@ -207,10 +207,11 @@ static int allocate_filesystem_keyring(struct super_block *sb)
* Release all encryption keys that have been added to the filesystem, along
* with the keyring that contains them.
*
* This is called at unmount time. The filesystem's underlying block device(s)
* are still available at this time; this is important because after user file
* accesses have been allowed, this function may need to evict keys from the
* keyslots of an inline crypto engine, which requires the block device(s).
* This is called at unmount time, after all potentially-encrypted inodes have
* been evicted. The filesystem's underlying block device(s) are still
* available at this time; this is important because after user file accesses
* have been allowed, this function may need to evict keys from the keyslots of
* an inline crypto engine, which requires the block device(s).
*/
void fscrypt_destroy_keyring(struct super_block *sb)
{
@ -227,12 +228,12 @@ void fscrypt_destroy_keyring(struct super_block *sb)
hlist_for_each_entry_safe(mk, tmp, bucket, mk_node) {
/*
* Since all inodes were already evicted, every key
* remaining in the keyring should have an empty inode
* list, and should only still be in the keyring due to
* the single active ref associated with ->mk_secret.
* There should be no structural refs beyond the one
* associated with the active ref.
* Since all potentially-encrypted inodes were already
* evicted, every key remaining in the keyring should
* have an empty inode list, and should only still be in
* the keyring due to the single active ref associated
* with ->mk_secret. There should be no structural refs
* beyond the one associated with the active ref.
*/
WARN_ON(refcount_read(&mk->mk_active_refs) != 1);
WARN_ON(refcount_read(&mk->mk_struct_refs) != 1);