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| 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/keyinfo.c | |
| parent | ff5d3a97075c65731a46453d36e75b9cf925e165 (diff) | |
| download | lwn-e37a784d8b6a1e726de5ddc7b4809c086a08db09.tar.gz lwn-e37a784d8b6a1e726de5ddc7b4809c086a08db09.zip | |
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/keyinfo.c')
| -rw-r--r-- | fs/crypto/keyinfo.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c index 322ce9686bdb..bf291c10c682 100644 --- a/fs/crypto/keyinfo.c +++ b/fs/crypto/keyinfo.c @@ -509,7 +509,7 @@ int fscrypt_get_encryption_info(struct inode *inode) u8 *raw_key = NULL; int res; - if (inode->i_crypt_info) + if (fscrypt_has_encryption_key(inode)) return 0; res = fscrypt_initialize(inode->i_sb->s_cop->flags); @@ -573,7 +573,7 @@ int fscrypt_get_encryption_info(struct inode *inode) if (res) goto out; - if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL) + if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) crypt_info = NULL; out: if (res == -ENOKEY) |