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:
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
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
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
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
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.
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