Re: [kernel-hardening] [PATCH v4 05/13] crypto/rng: ensure that the RNG is ready before using

2017-06-07 Thread Jason A. Donenfeld 
On Thu, Jun 8, 2017 at 2:41 AM, Theodore Ts'o  wrote:
> The use in keys/big_key is _being_ removed, so this commit is
> dependent on that commit landing, correct?  (Order matters, because
> otherwise we don't want to potentially screw up doing a kernel bisect
> and causing their kernel to deadlock during the boot while they are
> trying to track down an unreleated problem.)

Yes. It's actually landing with get_random_bytes, to avoid a
dependency problem when merging. After these both lands, I'll submit a
third changing that over to get_random_bytes_wait in the right place.

Re: [kernel-hardening] [PATCH v4 05/13] crypto/rng: ensure that the RNG is ready before using

2017-06-07 Thread Theodore Ts'o 
On Tue, Jun 06, 2017 at 07:47:56PM +0200, Jason A. Donenfeld wrote:
> Otherwise, we might be seeding the RNG using bad randomness, which is
> dangerous. The one use of this function from within the kernel -- not
> from userspace -- is being removed (keys/big_key), so that call site
> isn't relevant in assessing this.

The use in keys/big_key is _being_ removed, so this commit is
dependent on that commit landing, correct?  (Order matters, because
otherwise we don't want to potentially screw up doing a kernel bisect
and causing their kernel to deadlock during the boot while they are
trying to track down an unreleated problem.)

   - Ted

[PATCH v4 05/13] crypto/rng: ensure that the RNG is ready before using

2017-06-06 Thread Jason A. Donenfeld 
Otherwise, we might be seeding the RNG using bad randomness, which is
dangerous. The one use of this function from within the kernel -- not
from userspace -- is being removed (keys/big_key), so that call site
isn't relevant in assessing this.

Cc: Herbert Xu 
Signed-off-by: Jason A. Donenfeld 
---
 crypto/rng.c | 6 --
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/crypto/rng.c b/crypto/rng.c
index f46dac5288b9..e042437e64b4 100644
--- a/crypto/rng.c
+++ b/crypto/rng.c
@@ -48,12 +48,14 @@ int crypto_rng_reset(struct crypto_rng *tfm, const u8 
*seed, unsigned int slen)
if (!buf)
return -ENOMEM;
 
-   get_random_bytes(buf, slen);
+   err = get_random_bytes_wait(buf, slen);
+   if (err)
+   goto out;
seed = buf;
}
 
err = crypto_rng_alg(tfm)->seed(tfm, seed, slen);
-
+out:
kzfree(buf);
return err;
 }
-- 
2.13.0