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Message-ID: <20170608003116.zgznzb37ms7wj4vl@thunk.org>
Date: Wed, 7 Jun 2017 20:31:16 -0400
From: Theodore Ts'o <tytso@....edu>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
kernel-hardening@...ts.openwall.com,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
David Miller <davem@...emloft.net>,
Eric Biggers <ebiggers3@...il.com>,
David Howells <dhowells@...hat.com>,
Mimi Zohar <zohar@...ux.vnet.ibm.com>,
David Safford <safford@...ibm.com>
Subject: Re: [PATCH v4 04/13] security/keys: ensure RNG is seeded before use
On Tue, Jun 06, 2017 at 07:47:55PM +0200, Jason A. Donenfeld wrote:
> -static inline void key_alloc_serial(struct key *key)
> +static inline int key_alloc_serial(struct key *key)
> @@ -170,7 +168,7 @@ static inline void key_alloc_serial(struct key *key)
> rb_insert_color(&key->serial_node, &key_serial_tree);
>
> spin_unlock(&key_serial_lock);
> - return;
> + return 0;
>
> /* we found a key with the proposed serial number - walk the tree from
> * that point looking for the next unused serial number */
> @@ -314,7 +312,9 @@ struct key *key_alloc(struct key_type *type, const char *desc,
>
> /* publish the key by giving it a serial number */
> atomic_inc(&user->nkeys);
> - key_alloc_serial(key);
> + ret = key_alloc_serial(key);
> + if (ret < 0)
> + goto security_error;
>
> error:
> return key;
I'm guessing you changed key_alloc_serial() to return an int back when
you were thinking that you might use get_random_bytes_wait(), which
could return -ERESTARTSYS.
Now that you're not doing this, but using get_random_u32() instead,
there's no point to change the function signature of
key_alloc_serial() and add an error check in key_alloc() that will
never fail, right? That's just adding a dead code path. Which the
compiler can probably optimize away, but why make the code slightly
harder to read than necessasry?
- Ted
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