diff options
| author | Eric Biggers <ebiggers@google.com> | 2019-04-11 14:32:15 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-05-31 06:43:32 -0700 |
| commit | 8bcc53fb09779ea011623e7766f56e2ea24bdcf0 (patch) | |
| tree | a7a3959090210f78b52ec6c3bbd7c11eb4d577ad /include | |
| parent | d66a2891b79962cfa742967844da7fc5d9bdab87 (diff) | |
fscrypt: use READ_ONCE() to access ->i_crypt_info
[ Upstream commit e37a784d8b6a1e726de5ddc7b4809c086a08db09 ]
->i_crypt_info starts out NULL and may later be locklessly set to a
non-NULL value by the cmpxchg() in fscrypt_get_encryption_info().
But ->i_crypt_info is used directly, which technically is incorrect.
It's a data race, and it doesn't include the data dependency barrier
needed to safely dereference the pointer on at least one architecture.
Fix this by using READ_ONCE() instead. Note: we don't need to use
smp_load_acquire(), since dereferencing the pointer only requires a data
dependency barrier, which is already included in READ_ONCE(). We also
don't need READ_ONCE() in places where ->i_crypt_info is unconditionally
dereferenced, since it must have already been checked.
Also downgrade the cmpxchg() to cmpxchg_release(), since RELEASE
semantics are sufficient on the write side.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/fscrypt.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index e5194fc3983e..08246f068fd8 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -79,7 +79,8 @@ struct fscrypt_ctx { static inline bool fscrypt_has_encryption_key(const struct inode *inode) { - return (inode->i_crypt_info != NULL); + /* pairs with cmpxchg_release() in fscrypt_get_encryption_info() */ + return READ_ONCE(inode->i_crypt_info) != NULL; } static inline bool fscrypt_dummy_context_enabled(struct inode *inode) |