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authorEric Biggers <ebiggers@google.com>2019-04-11 14:32:15 -0700
committerTheodore Ts'o <tytso@mit.edu>2019-04-16 18:57:09 -0400
commite37a784d8b6a1e726de5ddc7b4809c086a08db09 (patch)
tree965d40cec69107aba4324f72db93d896b12d0737 /include/linux/fscrypt.h
parentff5d3a97075c65731a46453d36e75b9cf925e165 (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 'include/linux/fscrypt.h')
-rw-r--r--include/linux/fscrypt.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 6cf8a34523ff..ec8ab7108599 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)