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ANDROID: fscrypt: add key removal notifier chain

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Add a notifier chain so that sdcardfs can evict its dentries when an
fscrypt key is about to be removed.  This is needed for the
FS_IOC_REMOVE_ENCRYPTION_KEY ioctl to properly "lock" the encrypted
files underneath sdcardfs when an Android user is stopped.

This is meant to be a temporary patch carried as part of the sdcardfs
patchset until either we stop using sdcardfs, we get sdcardfs upstream,
or we find a way to provide what sdcardfs needs while also benefitting a
user upstream.

Bug: 120446149
Bug: 142275883
Test: see I83b451a2bc40c72fcd01d24aa5c34ad8de427534
Change-Id: Iec79775a71057d05a371d77da4a6541cb8e09cb7
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers 2019-10-09 14:35:48 -07:00
parent f04f84fdeb
commit 4932f53723
2 changed files with 36 additions and 0 deletions
fs/crypto
keyring.c
include/linux
fscrypt.h

22
fs/crypto/keyring.c
View file

@ -704,12 +704,34 @@ static int check_for_busy_inodes(struct super_block *sb,
return -EBUSY;
}
static BLOCKING_NOTIFIER_HEAD(fscrypt_key_removal_notifiers);
/*
* Register a function to be executed when the FS_IOC_REMOVE_ENCRYPTION_KEY
* ioctl has removed a key and is about to try evicting inodes.
*/
int fscrypt_register_key_removal_notifier(struct notifier_block *nb)
{
return blocking_notifier_chain_register(&fscrypt_key_removal_notifiers,
nb);
}
EXPORT_SYMBOL_GPL(fscrypt_register_key_removal_notifier);
int fscrypt_unregister_key_removal_notifier(struct notifier_block *nb)
{
return blocking_notifier_chain_unregister(&fscrypt_key_removal_notifiers,
nb);
}
EXPORT_SYMBOL_GPL(fscrypt_unregister_key_removal_notifier);
static int try_to_lock_encrypted_files(struct super_block *sb,
struct fscrypt_master_key *mk)
{
int err1;
int err2;
blocking_notifier_call_chain(&fscrypt_key_removal_notifiers, 0, NULL);
/*
* An inode can't be evicted while it is dirty or has dirty pages.
* Thus, we first have to clean the inodes in ->mk_decrypted_inodes.

14
include/linux/fscrypt.h
View file

@ -146,6 +146,8 @@ extern int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg);
extern int fscrypt_ioctl_remove_key_all_users(struct file *filp,
void __user *arg);
extern int fscrypt_ioctl_get_key_status(struct file *filp, void __user *arg);
extern int fscrypt_register_key_removal_notifier(struct notifier_block *nb);
extern int fscrypt_unregister_key_removal_notifier(struct notifier_block *nb);
/* keysetup.c */
extern int fscrypt_get_encryption_info(struct inode *);
@ -405,6 +407,18 @@ static inline int fscrypt_ioctl_get_key_status(struct file *filp,
return -EOPNOTSUPP;
}
static inline int fscrypt_register_key_removal_notifier(
struct notifier_block *nb)
{
return 0;
}
static inline int fscrypt_unregister_key_removal_notifier(
struct notifier_block *nb)
{
return 0;
}
/* keysetup.c */
static inline int fscrypt_get_encryption_info(struct inode *inode)
{