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Subject[PATCH] wusb: Stop using the stack for sg crypto scratch space
Date
Pointing an sg list at the stack is verboten and, with
CONFIG_VMAP_STACK=y, will malfunction. Use kmalloc for the wusb
crypto stack space instead.

Untested -- I'm not entirely convinced that this hardware exists in
the wild.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---

This is needed for 4.9 for wusb to have a chance of working on default x86
configurations.

drivers/usb/wusbcore/crypto.c | 59 +++++++++++++++++++++++++++----------------
1 file changed, 37 insertions(+), 22 deletions(-)

diff --git a/drivers/usb/wusbcore/crypto.c b/drivers/usb/wusbcore/crypto.c
index 33acd1599e99..2db79d64e66c 100644
--- a/drivers/usb/wusbcore/crypto.c
+++ b/drivers/usb/wusbcore/crypto.c
@@ -133,6 +133,13 @@ static void bytewise_xor(void *_bo, const void *_bi1, const void *_bi2,
bo[itr] = bi1[itr] ^ bi2[itr];
}

+/* Scratch space for MAC calculations. */
+struct wusb_mac_scratch {
+ struct aes_ccm_b0 b0;
+ struct aes_ccm_b1 b1;
+ struct aes_ccm_a ax;
+};
+
/*
* CC-MAC function WUSB1.0[6.5]
*
@@ -197,16 +204,15 @@ static void bytewise_xor(void *_bo, const void *_bi1, const void *_bi2,
* what sg[4] is for. Maybe there is a smarter way to do this.
*/
static int wusb_ccm_mac(struct crypto_skcipher *tfm_cbc,
- struct crypto_cipher *tfm_aes, void *mic,
+ struct crypto_cipher *tfm_aes,
+ struct wusb_mac_scratch *scratch,
+ void *mic,
const struct aes_ccm_nonce *n,
const struct aes_ccm_label *a, const void *b,
size_t blen)
{
int result = 0;
SKCIPHER_REQUEST_ON_STACK(req, tfm_cbc);
- struct aes_ccm_b0 b0;
- struct aes_ccm_b1 b1;
- struct aes_ccm_a ax;
struct scatterlist sg[4], sg_dst;
void *dst_buf;
size_t dst_size;
@@ -218,16 +224,17 @@ static int wusb_ccm_mac(struct crypto_skcipher *tfm_cbc,
* These checks should be compile time optimized out
* ensure @a fills b1's mac_header and following fields
*/
- WARN_ON(sizeof(*a) != sizeof(b1) - sizeof(b1.la));
- WARN_ON(sizeof(b0) != sizeof(struct aes_ccm_block));
- WARN_ON(sizeof(b1) != sizeof(struct aes_ccm_block));
- WARN_ON(sizeof(ax) != sizeof(struct aes_ccm_block));
+ WARN_ON(sizeof(*a) != sizeof(scratch->b1) - sizeof(scratch->b1.la));
+ WARN_ON(sizeof(scratch->b0) != sizeof(struct aes_ccm_block));
+ WARN_ON(sizeof(scratch->b1) != sizeof(struct aes_ccm_block));
+ WARN_ON(sizeof(scratch->ax) != sizeof(struct aes_ccm_block));

result = -ENOMEM;
zero_padding = blen % sizeof(struct aes_ccm_block);
if (zero_padding)
zero_padding = sizeof(struct aes_ccm_block) - zero_padding;
- dst_size = blen + sizeof(b0) + sizeof(b1) + zero_padding;
+ dst_size = blen + sizeof(scratch->b0) + sizeof(scratch->b1) +
+ zero_padding;
dst_buf = kzalloc(dst_size, GFP_KERNEL);
if (dst_buf == NULL) {
printk(KERN_ERR "E: can't alloc destination buffer\n");
@@ -237,9 +244,9 @@ static int wusb_ccm_mac(struct crypto_skcipher *tfm_cbc,
memset(iv, 0, sizeof(iv));

/* Setup B0 */
- b0.flags = 0x59; /* Format B0 */
- b0.ccm_nonce = *n;
- b0.lm = cpu_to_be16(0); /* WUSB1.0[6.5] sez l(m) is 0 */
+ scratch->b0.flags = 0x59; /* Format B0 */
+ scratch->b0.ccm_nonce = *n;
+ scratch->b0.lm = cpu_to_be16(0); /* WUSB1.0[6.5] sez l(m) is 0 */

/* Setup B1
*
@@ -248,12 +255,12 @@ static int wusb_ccm_mac(struct crypto_skcipher *tfm_cbc,
* 14'--after clarification, it means to use A's contents
* for MAC Header, EO, sec reserved and padding.
*/
- b1.la = cpu_to_be16(blen + 14);
- memcpy(&b1.mac_header, a, sizeof(*a));
+ scratch->b1.la = cpu_to_be16(blen + 14);
+ memcpy(&scratch->b1.mac_header, a, sizeof(*a));

sg_init_table(sg, ARRAY_SIZE(sg));
- sg_set_buf(&sg[0], &b0, sizeof(b0));
- sg_set_buf(&sg[1], &b1, sizeof(b1));
+ sg_set_buf(&sg[0], &scratch->b0, sizeof(scratch->b0));
+ sg_set_buf(&sg[1], &scratch->b1, sizeof(scratch->b1));
sg_set_buf(&sg[2], b, blen);
/* 0 if well behaved :) */
sg_set_buf(&sg[3], bzero, zero_padding);
@@ -278,11 +285,12 @@ static int wusb_ccm_mac(struct crypto_skcipher *tfm_cbc,
* POS Crypto API: size is assumed to be AES's block size.
* Thanks for documenting it -- tip taken from airo.c
*/
- ax.flags = 0x01; /* as per WUSB 1.0 spec */
- ax.ccm_nonce = *n;
- ax.counter = 0;
- crypto_cipher_encrypt_one(tfm_aes, (void *)&ax, (void *)&ax);
- bytewise_xor(mic, &ax, iv, 8);
+ scratch->ax.flags = 0x01; /* as per WUSB 1.0 spec */
+ scratch->ax.ccm_nonce = *n;
+ scratch->ax.counter = 0;
+ crypto_cipher_encrypt_one(tfm_aes, (void *)&scratch->ax,
+ (void *)&scratch->ax);
+ bytewise_xor(mic, &scratch->ax, iv, 8);
result = 8;
error_cbc_crypt:
kfree(dst_buf);
@@ -305,6 +313,7 @@ ssize_t wusb_prf(void *out, size_t out_size,
struct aes_ccm_nonce n = *_n;
struct crypto_skcipher *tfm_cbc;
struct crypto_cipher *tfm_aes;
+ struct wusb_mac_scratch *scratch;
u64 sfn = 0;
__le64 sfn_le;

@@ -331,17 +340,23 @@ ssize_t wusb_prf(void *out, size_t out_size,
printk(KERN_ERR "E: can't set AES key: %d\n", (int)result);
goto error_setkey_aes;
}
+ scratch = kmalloc(sizeof(*scratch), GFP_KERNEL);
+ if (!scratch)
+ goto error_alloc_scratch;

for (bitr = 0; bitr < (len + 63) / 64; bitr++) {
sfn_le = cpu_to_le64(sfn++);
memcpy(&n.sfn, &sfn_le, sizeof(n.sfn)); /* n.sfn++... */
- result = wusb_ccm_mac(tfm_cbc, tfm_aes, out + bytes,
+ result = wusb_ccm_mac(tfm_cbc, tfm_aes, scratch, out + bytes,
&n, a, b, blen);
if (result < 0)
goto error_ccm_mac;
bytes += result;
}
result = bytes;
+
+ kfree(scratch);
+error_alloc_scratch:
error_ccm_mac:
error_setkey_aes:
crypto_free_cipher(tfm_aes);
--
2.7.4
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