fscrypt: avoid data race on fscrypt_mode::logged_impl_name
The access to logged_impl_name is technically a data race, which tools
like KCSAN could complain about in the future. See:
https://github.com/google/ktsan/wiki/READ_ONCE-and-WRITE_ONCE
Fix by using xchg(), which also ensures that only one thread does the
logging.
This also required switching from bool to int, to avoid a build error on
the RISC-V architecture which doesn't implement xchg on bytes.
Signed-off-by: Eric Biggers <ebiggers@google.com>
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index dacf8fc..d9a3e86 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -435,7 +435,7 @@
const char *cipher_str;
int keysize;
int ivsize;
- bool logged_impl_name;
+ int logged_impl_name;
};
static inline bool
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index b03b336..28bc2da 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -81,15 +81,13 @@
mode->cipher_str, PTR_ERR(tfm));
return tfm;
}
- if (unlikely(!mode->logged_impl_name)) {
+ if (!xchg(&mode->logged_impl_name, 1)) {
/*
* fscrypt performance can vary greatly depending on which
* crypto algorithm implementation is used. Help people debug
* performance problems by logging the ->cra_driver_name the
- * first time a mode is used. Note that multiple threads can
- * race here, but it doesn't really matter.
+ * first time a mode is used.
*/
- mode->logged_impl_name = true;
pr_info("fscrypt: %s using implementation \"%s\"\n",
mode->friendly_name,
crypto_skcipher_alg(tfm)->base.cra_driver_name);
