[PATCH v2] keys/encrypted: Fix two crypto-on-the-stack bugs

Andy Lutomirski
2016-12-14T02:48:13Z

The driver put a constant buffer of all zeros on the stack and
pointed a scatterlist entry at it in two places. This doesn't work
with virtual stacks. Use ZERO_PAGE instead.

Cc: stable@vger.kernel.org # 4.9 only
Reported-by: Eric Biggers <ebiggers3@gmail.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
security/keys/encrypted-keys/encrypted.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index 17a06105ccb6..e963160ed26a 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -481,7 +481,6 @@ static int derived_key_encrypt(struct encrypted_key_payload *epayload,
unsigned int encrypted_datalen;
u8 iv[AES_BLOCK_SIZE];
unsigned int padlen;
- char pad[16];
int ret;

encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
@@ -493,11 +492,10 @@ static int derived_key_encrypt(struct encrypted_key_payload *epayload,
goto out;
dump_decrypted_data(epayload);

- memset(pad, 0, sizeof pad);
sg_init_table(sg_in, 2);
sg_set_buf(&sg_in[0], epayload->decrypted_data,
epayload->decrypted_datalen);
- sg_set_buf(&sg_in[1], pad, padlen);
+ sg_set_page(&sg_in[1], ZERO_PAGE(0), padlen, 0);

sg_init_table(sg_out, 1);
sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
@@ -584,7 +582,6 @@ static int derived_key_decrypt(struct encrypted_key_payload *epayload,
struct skcipher_request *req;
unsigned int encrypted_datalen;
u8 iv[AES_BLOCK_SIZE];
- char pad[16];
int ret;

encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
@@ -594,13 +591,12 @@ static int derived_key_decrypt(struct encrypted_key_payload *epayload,
goto out;
dump_encrypted_data(epayload, encrypted_datalen);

- memset(pad, 0, sizeof pad);
sg_init_table(sg_in, 1);
sg_init_table(sg_out, 2);
sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
sg_set_buf(&sg_out[0], epayload->decrypted_data,
epayload->decrypted_datalen);
- sg_set_buf(&sg_out[1], pad, sizeof pad);
+ sg_set_buf(&sg_out[1], empty_zero_page, 16);

memcpy(iv, epayload->iv, sizeof(iv));
skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
--
2.9.3