| Message ID | 20180308215702.GA9902@beast (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 03/08/2018 11:57 PM, Kees Cook wrote: > On the quest to remove all VLAs from the kernel[1], this switches to > a pair of kmalloc regions instead of using the stack. This also moves > the get_random_bytes() after all allocations (and drops the needless > "nbytes" variable). > > [1]https://lkml.org/lkml/2018/3/7/621 > > Signed-off-by: Kees Cook<keescook@chromium.org> Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
On Thu, Mar 08, 2018 at 01:57:02PM -0800, Kees Cook wrote: > On the quest to remove all VLAs from the kernel[1], this switches to > a pair of kmalloc regions instead of using the stack. This also moves > the get_random_bytes() after all allocations (and drops the needless > "nbytes" variable). > > [1] https://lkml.org/lkml/2018/3/7/621 > > Signed-off-by: Kees Cook <keescook@chromium.org> Patch applied. Thanks.
On Fri, Mar 16, 2018 at 8:56 AM, Herbert Xu <herbert@gondor.apana.org.au> wrote: > On Thu, Mar 08, 2018 at 01:57:02PM -0800, Kees Cook wrote: >> On the quest to remove all VLAs from the kernel[1], this switches to >> a pair of kmalloc regions instead of using the stack. This also moves >> the get_random_bytes() after all allocations (and drops the needless >> "nbytes" variable). >> >> [1] https://lkml.org/lkml/2018/3/7/621 >> >> Signed-off-by: Kees Cook <keescook@chromium.org> > > Patch applied. Thanks. Hi, sorry for the noise on this one: I messed up looking at the ecc code (I confused myself into thinking there was only a single instance of the problem). The applied patch is both incomplete and inefficient. I have a much simpler solution, and I'll send that with a revert... -Kees
diff --git a/crypto/ecc.c b/crypto/ecc.c index 18f32f2a5e1c..9c066b5ac12d 100644 --- a/crypto/ecc.c +++ b/crypto/ecc.c @@ -1025,9 +1025,7 @@ int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits, { int ret = 0; struct ecc_point *product, *pk; - u64 priv[ndigits]; - u64 rand_z[ndigits]; - unsigned int nbytes; + u64 *priv, *rand_z; const struct ecc_curve *curve = ecc_get_curve(curve_id); if (!private_key || !public_key || !curve) { @@ -1035,14 +1033,22 @@ int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits, goto out; } - nbytes = ndigits << ECC_DIGITS_TO_BYTES_SHIFT; + priv = kmalloc_array(ndigits, sizeof(*priv), GFP_KERNEL); + if (!priv) { + ret = -ENOMEM; + goto out; + } - get_random_bytes(rand_z, nbytes); + rand_z = kmalloc_array(ndigits, sizeof(*rand_z), GFP_KERNEL); + if (!rand_z) { + ret = -ENOMEM; + goto kfree_out; + } pk = ecc_alloc_point(ndigits); if (!pk) { ret = -ENOMEM; - goto out; + goto kfree_out; } product = ecc_alloc_point(ndigits); @@ -1051,6 +1057,8 @@ int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits, goto err_alloc_product; } + get_random_bytes(rand_z, ndigits << ECC_DIGITS_TO_BYTES_SHIFT); + ecc_swap_digits(public_key, pk->x, ndigits); ecc_swap_digits(&public_key[ndigits], pk->y, ndigits); ecc_swap_digits(private_key, priv, ndigits); @@ -1065,6 +1073,9 @@ int crypto_ecdh_shared_secret(unsigned int curve_id, unsigned int ndigits, ecc_free_point(product); err_alloc_product: ecc_free_point(pk); +kfree_out: + kzfree(priv); + kzfree(rand_z); out: return ret; }
On the quest to remove all VLAs from the kernel[1], this switches to a pair of kmalloc regions instead of using the stack. This also moves the get_random_bytes() after all allocations (and drops the needless "nbytes" variable). [1] https://lkml.org/lkml/2018/3/7/621 Signed-off-by: Kees Cook <keescook@chromium.org> --- crypto/ecc.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-)