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authorEric Biggers <ebiggers@google.com>2019-10-21 13:49:03 -0700
committerEric Biggers <ebiggers@google.com>2019-11-06 12:33:15 -0800
commitff73c2c016f8569b728eb1e9ebfab383545e4d65 (patch)
tree878f712c354b45c9d251da651ab4b3440e175ba2 /fs/crypto
parent065ab4c4701ff6e28785eb8172925fc3068cc15e (diff)
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>
Diffstat (limited to 'fs/crypto')
-rw-r--r--fs/crypto/fscrypt_private.h2
-rw-r--r--fs/crypto/keysetup.c6
2 files changed, 3 insertions, 5 deletions
diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
index dacf8fcbac3b..d9a3e8614049 100644
--- a/fs/crypto/fscrypt_private.h
+++ b/fs/crypto/fscrypt_private.h
@@ -435,7 +435,7 @@ struct fscrypt_mode {
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 b03b33643e4b..28bc2da9be3c 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -81,15 +81,13 @@ struct crypto_skcipher *fscrypt_allocate_skcipher(struct fscrypt_mode *mode,
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);