* [PATCH] crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS
@ 2021-03-22 5:07 Eric Biggers
2021-03-22 5:45 ` Dan Carpenter
2021-04-02 9:03 ` Herbert Xu
0 siblings, 2 replies; 6+ messages in thread
From: Eric Biggers @ 2021-03-22 5:07 UTC (permalink / raw)
To: linux-crypto; +Cc: Dan Carpenter, Neil Horman, Corentin Labbe, stable
From: Eric Biggers <ebiggers@google.com>
crypto_stats_get() is a no-op when the kernel is compiled without
CONFIG_CRYPTO_STATS, so pairing it with crypto_alg_put() unconditionally
(as crypto_rng_reset() does) is wrong.
Fix this by moving the call to crypto_stats_get() to just before the
actual algorithm operation which might need it. This makes it always
paired with crypto_stats_rng_seed().
Fixes: eed74b3eba9e ("crypto: rng - Fix a refcounting bug in crypto_rng_reset()")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
crypto/rng.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)
diff --git a/crypto/rng.c b/crypto/rng.c
index a888d84b524a4..fea082b25fe4b 100644
--- a/crypto/rng.c
+++ b/crypto/rng.c
@@ -34,22 +34,18 @@ int crypto_rng_reset(struct crypto_rng *tfm, const u8 *seed, unsigned int slen)
u8 *buf = NULL;
int err;
- crypto_stats_get(alg);
if (!seed && slen) {
buf = kmalloc(slen, GFP_KERNEL);
- if (!buf) {
- crypto_alg_put(alg);
+ if (!buf)
return -ENOMEM;
- }
err = get_random_bytes_wait(buf, slen);
- if (err) {
- crypto_alg_put(alg);
+ if (err)
goto out;
- }
seed = buf;
}
+ crypto_stats_get(alg);
err = crypto_rng_alg(tfm)->seed(tfm, seed, slen);
crypto_stats_rng_seed(alg, err);
out:
--
2.31.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS
2021-03-22 5:07 [PATCH] crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS Eric Biggers
@ 2021-03-22 5:45 ` Dan Carpenter
2021-03-22 6:00 ` Eric Biggers
2021-04-02 9:03 ` Herbert Xu
1 sibling, 1 reply; 6+ messages in thread
From: Dan Carpenter @ 2021-03-22 5:45 UTC (permalink / raw)
To: Eric Biggers; +Cc: linux-crypto, Neil Horman, Corentin Labbe, stable
On Sun, Mar 21, 2021 at 10:07:48PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> crypto_stats_get() is a no-op when the kernel is compiled without
> CONFIG_CRYPTO_STATS, so pairing it with crypto_alg_put() unconditionally
> (as crypto_rng_reset() does) is wrong.
>
Presumably the intention was that _get() and _put() should always pair.
It's really ugly and horrible that they don't. We could have
predicted bug like this would happen and will continue to happen until
the crypto_stats_get() is renamed.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS
2021-03-22 5:45 ` Dan Carpenter
@ 2021-03-22 6:00 ` Eric Biggers
2021-03-22 7:33 ` Dan Carpenter
0 siblings, 1 reply; 6+ messages in thread
From: Eric Biggers @ 2021-03-22 6:00 UTC (permalink / raw)
To: Dan Carpenter; +Cc: linux-crypto, Neil Horman, Corentin Labbe, stable
On Mon, Mar 22, 2021 at 08:45:22AM +0300, Dan Carpenter wrote:
> On Sun, Mar 21, 2021 at 10:07:48PM -0700, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@google.com>
> >
> > crypto_stats_get() is a no-op when the kernel is compiled without
> > CONFIG_CRYPTO_STATS, so pairing it with crypto_alg_put() unconditionally
> > (as crypto_rng_reset() does) is wrong.
> >
>
> Presumably the intention was that _get() and _put() should always pair.
> It's really ugly and horrible that they don't. We could have
> predicted bug like this would happen and will continue to happen until
> the crypto_stats_get() is renamed.
>
Well, the crypto stats stuff has always been pretty broken, so I don't think
people have looked at it too closely. Currently crypto_stats_get() pairs with
one of the functions that tallies the statistics, such as
crypto_stats_rng_seed() or crypto_stats_aead_encrypt(). What change are you
suggesting, exactly? Maybe moving the conditional crypto_alg_put() into a new
function crypto_stats_put() and moving it into the callers? Or do you think the
functions should just be renamed to something like crypto_stats_begin() and
crypto_stats_end_{rng_seed,aead_encrypt}()?
Another issue is that a lot of operations (such as the rng one in question here)
don't actually need the get/put at all because they are never asynchronous. I
didn't aim to address that in my patch though...
- Eric
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS
2021-03-22 6:00 ` Eric Biggers
@ 2021-03-22 7:33 ` Dan Carpenter
2021-03-22 12:13 ` LABBE Corentin
0 siblings, 1 reply; 6+ messages in thread
From: Dan Carpenter @ 2021-03-22 7:33 UTC (permalink / raw)
To: Eric Biggers; +Cc: linux-crypto, Neil Horman, Corentin Labbe, stable
On Sun, Mar 21, 2021 at 11:00:09PM -0700, Eric Biggers wrote:
> On Mon, Mar 22, 2021 at 08:45:22AM +0300, Dan Carpenter wrote:
> > On Sun, Mar 21, 2021 at 10:07:48PM -0700, Eric Biggers wrote:
> > > From: Eric Biggers <ebiggers@google.com>
> > >
> > > crypto_stats_get() is a no-op when the kernel is compiled without
> > > CONFIG_CRYPTO_STATS, so pairing it with crypto_alg_put() unconditionally
> > > (as crypto_rng_reset() does) is wrong.
> > >
> >
> > Presumably the intention was that _get() and _put() should always pair.
> > It's really ugly and horrible that they don't. We could have
> > predicted bug like this would happen and will continue to happen until
> > the crypto_stats_get() is renamed.
> >
>
> Well, the crypto stats stuff has always been pretty broken, so I don't think
> people have looked at it too closely. Currently crypto_stats_get() pairs with
> one of the functions that tallies the statistics, such as
> crypto_stats_rng_seed() or crypto_stats_aead_encrypt(). What change are you
> suggesting, exactly? Maybe moving the conditional crypto_alg_put() into a new
> function crypto_stats_put() and moving it into the callers? Or do you think the
> functions should just be renamed to something like crypto_stats_begin() and
> crypto_stats_end_{rng_seed,aead_encrypt}()?
To be honest, I misread the crypto_alg_put() thinking that it was
crypto_*stats*_put(). My favourite fix would be to introduce a
crypto_stats_put() which is a mirror of crypto_stats_get() and ifdeffed
out if we don't have CONFIG_CRYPTO_STATS.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS
2021-03-22 7:33 ` Dan Carpenter
@ 2021-03-22 12:13 ` LABBE Corentin
0 siblings, 0 replies; 6+ messages in thread
From: LABBE Corentin @ 2021-03-22 12:13 UTC (permalink / raw)
To: Dan Carpenter; +Cc: Eric Biggers, linux-crypto, Neil Horman, stable
Le Mon, Mar 22, 2021 at 10:33:01AM +0300, Dan Carpenter a écrit :
> On Sun, Mar 21, 2021 at 11:00:09PM -0700, Eric Biggers wrote:
> > On Mon, Mar 22, 2021 at 08:45:22AM +0300, Dan Carpenter wrote:
> > > On Sun, Mar 21, 2021 at 10:07:48PM -0700, Eric Biggers wrote:
> > > > From: Eric Biggers <ebiggers@google.com>
> > > >
> > > > crypto_stats_get() is a no-op when the kernel is compiled without
> > > > CONFIG_CRYPTO_STATS, so pairing it with crypto_alg_put() unconditionally
> > > > (as crypto_rng_reset() does) is wrong.
> > > >
> > >
> > > Presumably the intention was that _get() and _put() should always pair.
> > > It's really ugly and horrible that they don't. We could have
> > > predicted bug like this would happen and will continue to happen until
> > > the crypto_stats_get() is renamed.
> > >
> >
> > Well, the crypto stats stuff has always been pretty broken, so I don't think
> > people have looked at it too closely. Currently crypto_stats_get() pairs with
> > one of the functions that tallies the statistics, such as
> > crypto_stats_rng_seed() or crypto_stats_aead_encrypt(). What change are you
> > suggesting, exactly? Maybe moving the conditional crypto_alg_put() into a new
> > function crypto_stats_put() and moving it into the callers? Or do you think the
> > functions should just be renamed to something like crypto_stats_begin() and
> > crypto_stats_end_{rng_seed,aead_encrypt}()?
>
> To be honest, I misread the crypto_alg_put() thinking that it was
> crypto_*stats*_put(). My favourite fix would be to introduce a
> crypto_stats_put() which is a mirror of crypto_stats_get() and ifdeffed
> out if we don't have CONFIG_CRYPTO_STATS.
>
I agree it will be better.
I can work on adding crypto_stats_put() if you want.
Regards
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS
2021-03-22 5:07 [PATCH] crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS Eric Biggers
2021-03-22 5:45 ` Dan Carpenter
@ 2021-04-02 9:03 ` Herbert Xu
1 sibling, 0 replies; 6+ messages in thread
From: Herbert Xu @ 2021-04-02 9:03 UTC (permalink / raw)
To: Eric Biggers; +Cc: linux-crypto, dan.carpenter, nhorman, clabbe, stable
Eric Biggers <ebiggers@kernel.org> wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> crypto_stats_get() is a no-op when the kernel is compiled without
> CONFIG_CRYPTO_STATS, so pairing it with crypto_alg_put() unconditionally
> (as crypto_rng_reset() does) is wrong.
>
> Fix this by moving the call to crypto_stats_get() to just before the
> actual algorithm operation which might need it. This makes it always
> paired with crypto_stats_rng_seed().
>
> Fixes: eed74b3eba9e ("crypto: rng - Fix a refcounting bug in crypto_rng_reset()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
> crypto/rng.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
Patch applied. Thanks.
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
^ permalink raw reply [flat|nested] 6+ messages in thread
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2021-03-22 5:07 [PATCH] crypto: rng - fix crypto_rng_reset() refcounting when !CRYPTO_STATS Eric Biggers
2021-03-22 5:45 ` Dan Carpenter
2021-03-22 6:00 ` Eric Biggers
2021-03-22 7:33 ` Dan Carpenter
2021-03-22 12:13 ` LABBE Corentin
2021-04-02 9:03 ` Herbert Xu
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