fscrypto: make XTS tweak initialization endian-independent (fb445437) · Commits · 戴 / test

The XTS tweak (or IV) was initialized differently on little endian and big endian systems. Because the ciphertext depends on the XTS tweak, it was not possible to use an encrypted filesystem created by a little endian system on a big endian system and vice versa, even if they shared the same PAGE_SIZE. Fix this by always using little endian. This will break hypothetical big endian users of ext4 or f2fs encryption. However, all users we are aware of are little endian, and it's believed that "real" big endian users are unlikely to exist yet. So this might as well be fixed now before it's too late. Signed-off-by:

Eric Biggers <ebiggers@google.com> Signed-off-by:

Theodore Ts'o <tytso@mit.edu> Cc: stable@vger.kernel.org

fs/crypto/crypto.c

+8 −7

Original line number	Diff line number	Diff line
		@@ -151,7 +151,10 @@ static int do_page_crypto(struct inode *inode,
		struct page src_page, struct page dest_page,
		gfp_t gfp_flags)
		{
		u8 xts_tweak[FS_XTS_TWEAK_SIZE];
		struct {
		__le64 index;
		u8 padding[FS_XTS_TWEAK_SIZE - sizeof(__le64)];
		} xts_tweak;
		struct skcipher_request *req = NULL;
		DECLARE_FS_COMPLETION_RESULT(ecr);
		struct scatterlist dst, src;
		@@ -171,17 +174,15 @@ static int do_page_crypto(struct inode *inode,
		req, CRYPTO_TFM_REQ_MAY_BACKLOG \| CRYPTO_TFM_REQ_MAY_SLEEP,
		page_crypt_complete, &ecr);

		BUILD_BUG_ON(FS_XTS_TWEAK_SIZE < sizeof(index));
		memcpy(xts_tweak, &index, sizeof(index));
		memset(&xts_tweak[sizeof(index)], 0,
		FS_XTS_TWEAK_SIZE - sizeof(index));
		BUILD_BUG_ON(sizeof(xts_tweak) != FS_XTS_TWEAK_SIZE);
		xts_tweak.index = cpu_to_le64(index);
		memset(xts_tweak.padding, 0, sizeof(xts_tweak.padding));

		sg_init_table(&dst, 1);
		sg_set_page(&dst, dest_page, PAGE_SIZE, 0);
		sg_init_table(&src, 1);
		sg_set_page(&src, src_page, PAGE_SIZE, 0);
		skcipher_request_set_crypt(req, &src, &dst, PAGE_SIZE,
		xts_tweak);
		skcipher_request_set_crypt(req, &src, &dst, PAGE_SIZE, &xts_tweak);
		if (rw == FS_DECRYPT)
		res = crypto_skcipher_decrypt(req);
		else

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