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fscrypto: make XTS tweak initialization endian-independent

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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
This commit is contained in:
Eric Biggers 2016-10-12 23:30:16 -04:00 committed by Theodore Ts'o
parent c4704a4fbe
commit fb4454376d
1 changed files with 8 additions and 7 deletions
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15
fs/crypto/crypto.c
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@ -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