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Commit 01b9d842 authored by Eric Biggers's avatar Eric Biggers Committed by Jaegeuk Kim
Browse files

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: default avatarEric Biggers <ebiggers@google.com>
parent f6711b42

fs/crypto/fscrypt_private.h

+1 −1
Original line number Diff line number Diff line
@@ -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

fs/crypto/keysetup.c

+2 −4
Original line number Diff line number Diff line
@@ -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);