diff options
| author | Eric Biggers <ebiggers@google.com> | 2019-04-11 14:32:15 -0700 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2019-04-16 18:57:09 -0400 |
| commit | e37a784d8b6a1e726de5ddc7b4809c086a08db09 (patch) | |
| tree | 965d40cec69107aba4324f72db93d896b12d0737 /fs/crypto/policy.c | |
| parent | ff5d3a97075c65731a46453d36e75b9cf925e165 (diff) | |
fscrypt: use READ_ONCE() to access ->i_crypt_info
->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>
Diffstat (limited to 'fs/crypto/policy.c')
| -rw-r--r-- | fs/crypto/policy.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index bd7eaf9b3f00..d536889ac31b 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -194,8 +194,8 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) res = fscrypt_get_encryption_info(child); if (res) return 0; - parent_ci = parent->i_crypt_info; - child_ci = child->i_crypt_info; + parent_ci = READ_ONCE(parent->i_crypt_info); + child_ci = READ_ONCE(child->i_crypt_info); if (parent_ci && child_ci) { return memcmp(parent_ci->ci_master_key_descriptor, @@ -246,7 +246,7 @@ int fscrypt_inherit_context(struct inode *parent, struct inode *child, if (res < 0) return res; - ci = parent->i_crypt_info; + ci = READ_ONCE(parent->i_crypt_info); if (ci == NULL) return -ENOKEY; |