[PATCH][next] KEYS: trusted: Fix missing null return from kzalloc call

[PATCH][next] KEYS: trusted: Fix missing null return from kzalloc call

[Colin King]

From: Colin Ian King <colin.king@canonical.com>

The kzalloc call can return null with the GFP_KERNEL flag so
add a null check and exit via a new error exit label. Use the
same exit error label for another error path too.

Addresses-Coverity: ("Dereference null return value")
Fixes: 830027e2cb55 ("KEYS: trusted: Add generic trusted keys framework")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 security/keys/trusted-keys/trusted_core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
index ec3a066a4b42..90774793f0b1 100644
--- a/security/keys/trusted-keys/trusted_core.c
+++ b/security/keys/trusted-keys/trusted_core.c
@@ -116,11 +116,13 @@ static struct trusted_key_payload *trusted_payload_alloc(struct key *key)
 
 	ret = key_payload_reserve(key, sizeof(*p));
 	if (ret < 0)
-		return p;
+		goto err;
 	p = kzalloc(sizeof(*p), GFP_KERNEL);
+	if (!p)
+		goto err;
 
 	p->migratable = migratable;
-
+err:
 	return p;
 }
 
-- 
2.30.2

Re: [PATCH][next] KEYS: trusted: Fix missing null return from kzalloc call

[James Bottomley]

On Mon, 2021-04-12 at 17:01 +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The kzalloc call can return null with the GFP_KERNEL flag so
> add a null check and exit via a new error exit label. Use the
> same exit error label for another error path too.
> 
> Addresses-Coverity: ("Dereference null return value")
> Fixes: 830027e2cb55 ("KEYS: trusted: Add generic trusted keys
> framework")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  security/keys/trusted-keys/trusted_core.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/security/keys/trusted-keys/trusted_core.c
> b/security/keys/trusted-keys/trusted_core.c
> index ec3a066a4b42..90774793f0b1 100644
> --- a/security/keys/trusted-keys/trusted_core.c
> +++ b/security/keys/trusted-keys/trusted_core.c
> @@ -116,11 +116,13 @@ static struct trusted_key_payload
> *trusted_payload_alloc(struct key *key)
>  
>  	ret = key_payload_reserve(key, sizeof(*p));
>  	if (ret < 0)
> -		return p;
> +		goto err;
>  	p = kzalloc(sizeof(*p), GFP_KERNEL);
> +	if (!p)
> +		goto err;
>  
>  	p->migratable = migratable;
> -
> +err:
>  	return p;

This is clearly a code migration bug in 

commit 251c85bd106099e6f388a89e88e12d14de2c9cda
Author: Sumit Garg <sumit.garg@linaro.org>
Date:   Mon Mar 1 18:41:24 2021 +0530

    KEYS: trusted: Add generic trusted keys framework

Which has for addition to trusted_core.c:

+static struct trusted_key_payload *trusted_payload_alloc(struct key
*key)
+{
+       struct trusted_key_payload *p = NULL;
+       int ret;
+
+       ret = key_payload_reserve(key, sizeof(*p));
+       if (ret < 0)
+               return p;
+       p = kzalloc(sizeof(*p), GFP_KERNEL);
+
+       p->migratable = migratable;
+
+       return p;
+}

And for trusted_tpm1.c:

-static struct trusted_key_payload *trusted_payload_alloc(struct key
*key)
-{
-       struct trusted_key_payload *p = NULL;
-       int ret;
-
-       ret = key_payload_reserve(key, sizeof *p);
-       if (ret < 0)
-               return p;
-       p = kzalloc(sizeof *p, GFP_KERNEL);
-       if (p)
-               p->migratable = 1; /* migratable by default */
-       return p;
-}

The trusted_tpm1.c code was correct and we got this bug introduced by
what should have been a simple cut and paste ... how did that happen? 
And therefore, how safe is the rest of the extraction into
trusted_core.c?

James

Re: [PATCH][next] KEYS: trusted: Fix missing null return from kzalloc call

[Colin Ian King]

On 12/04/2021 17:48, James Bottomley wrote:
> On Mon, 2021-04-12 at 17:01 +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.com>
>>
>> The kzalloc call can return null with the GFP_KERNEL flag so
>> add a null check and exit via a new error exit label. Use the
>> same exit error label for another error path too.
>>
>> Addresses-Coverity: ("Dereference null return value")
>> Fixes: 830027e2cb55 ("KEYS: trusted: Add generic trusted keys
>> framework")
>> Signed-off-by: Colin Ian King <colin.king@canonical.com>
>> ---
>>  security/keys/trusted-keys/trusted_core.c | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/security/keys/trusted-keys/trusted_core.c
>> b/security/keys/trusted-keys/trusted_core.c
>> index ec3a066a4b42..90774793f0b1 100644
>> --- a/security/keys/trusted-keys/trusted_core.c
>> +++ b/security/keys/trusted-keys/trusted_core.c
>> @@ -116,11 +116,13 @@ static struct trusted_key_payload
>> *trusted_payload_alloc(struct key *key)
>>  
>>  	ret = key_payload_reserve(key, sizeof(*p));
>>  	if (ret < 0)
>> -		return p;
>> +		goto err;
>>  	p = kzalloc(sizeof(*p), GFP_KERNEL);
>> +	if (!p)
>> +		goto err;
>>  
>>  	p->migratable = migratable;
>> -
>> +err:
>>  	return p;
> 
> This is clearly a code migration bug in 
> 
> commit 251c85bd106099e6f388a89e88e12d14de2c9cda
> Author: Sumit Garg <sumit.garg@linaro.org>
> Date:   Mon Mar 1 18:41:24 2021 +0530
> 
>     KEYS: trusted: Add generic trusted keys framework
> 
> Which has for addition to trusted_core.c:
> 
> +static struct trusted_key_payload *trusted_payload_alloc(struct key
> *key)
> +{
> +       struct trusted_key_payload *p = NULL;
> +       int ret;
> +
> +       ret = key_payload_reserve(key, sizeof(*p));
> +       if (ret < 0)
> +               return p;
> +       p = kzalloc(sizeof(*p), GFP_KERNEL);
> +
> +       p->migratable = migratable;
> +
> +       return p;
> +}
> 
> And for trusted_tpm1.c:
> 
> -static struct trusted_key_payload *trusted_payload_alloc(struct key
> *key)
> -{
> -       struct trusted_key_payload *p = NULL;
> -       int ret;
> -
> -       ret = key_payload_reserve(key, sizeof *p);
> -       if (ret < 0)
> -               return p;
> -       p = kzalloc(sizeof *p, GFP_KERNEL);
> -       if (p)
> -               p->migratable = 1; /* migratable by default */
> -       return p;
> -}
> 
> The trusted_tpm1.c code was correct and we got this bug introduced by
> what should have been a simple cut and paste ... how did that happen? 
> And therefore, how safe is the rest of the extraction into
> trusted_core.c?
> 

fortunately it gets caught by static analysis, but it does make me also
concerned about what else has changed and how this gets through review.

> James
> 
> 

Re: [PATCH][next] KEYS: trusted: Fix missing null return from kzalloc call

[Sumit Garg]

On Mon, 12 Apr 2021 at 22:34, Colin Ian King <colin.king@canonical.com> wrote:
>
> On 12/04/2021 17:48, James Bottomley wrote:
> > On Mon, 2021-04-12 at 17:01 +0100, Colin King wrote:
> >> From: Colin Ian King <colin.king@canonical.com>
> >>
> >> The kzalloc call can return null with the GFP_KERNEL flag so
> >> add a null check and exit via a new error exit label. Use the
> >> same exit error label for another error path too.
> >>
> >> Addresses-Coverity: ("Dereference null return value")
> >> Fixes: 830027e2cb55 ("KEYS: trusted: Add generic trusted keys
> >> framework")
> >> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> >> ---
> >>  security/keys/trusted-keys/trusted_core.c | 6 ++++--
> >>  1 file changed, 4 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/security/keys/trusted-keys/trusted_core.c
> >> b/security/keys/trusted-keys/trusted_core.c
> >> index ec3a066a4b42..90774793f0b1 100644
> >> --- a/security/keys/trusted-keys/trusted_core.c
> >> +++ b/security/keys/trusted-keys/trusted_core.c
> >> @@ -116,11 +116,13 @@ static struct trusted_key_payload
> >> *trusted_payload_alloc(struct key *key)
> >>
> >>      ret = key_payload_reserve(key, sizeof(*p));
> >>      if (ret < 0)
> >> -            return p;
> >> +            goto err;
> >>      p = kzalloc(sizeof(*p), GFP_KERNEL);
> >> +    if (!p)
> >> +            goto err;
> >>
> >>      p->migratable = migratable;
> >> -
> >> +err:
> >>      return p;
> >
> > This is clearly a code migration bug in
> >
> > commit 251c85bd106099e6f388a89e88e12d14de2c9cda
> > Author: Sumit Garg <sumit.garg@linaro.org>
> > Date:   Mon Mar 1 18:41:24 2021 +0530
> >
> >     KEYS: trusted: Add generic trusted keys framework
> >
> > Which has for addition to trusted_core.c:
> >
> > +static struct trusted_key_payload *trusted_payload_alloc(struct key
> > *key)
> > +{
> > +       struct trusted_key_payload *p = NULL;
> > +       int ret;
> > +
> > +       ret = key_payload_reserve(key, sizeof(*p));
> > +       if (ret < 0)
> > +               return p;
> > +       p = kzalloc(sizeof(*p), GFP_KERNEL);
> > +
> > +       p->migratable = migratable;
> > +
> > +       return p;
> > +}
> >
> > And for trusted_tpm1.c:
> >
> > -static struct trusted_key_payload *trusted_payload_alloc(struct key
> > *key)
> > -{
> > -       struct trusted_key_payload *p = NULL;
> > -       int ret;
> > -
> > -       ret = key_payload_reserve(key, sizeof *p);
> > -       if (ret < 0)
> > -               return p;
> > -       p = kzalloc(sizeof *p, GFP_KERNEL);
> > -       if (p)
> > -               p->migratable = 1; /* migratable by default */
> > -       return p;
> > -}
> >
> > The trusted_tpm1.c code was correct and we got this bug introduced by
> > what should have been a simple cut and paste ... how did that happen?

It was a little more than just cut and paste where I did generalized
"migratable" flag to be provided by the corresponding trust source's
ops struct.

> > And therefore, how safe is the rest of the extraction into
> > trusted_core.c?
> >
>
> fortunately it gets caught by static analysis, but it does make me also
> concerned about what else has changed and how this gets through review.
>

I agree that extraction into trusted_core.c was a complex change but
this patch has been up for review for almost 2 years [1]. And
extensive testing can't catch this sort of bug as allocation wouldn't
normally fail.

[1] https://lwn.net/Articles/795416/

-Sumit

> > James
> >
> >
>

Re: [PATCH][next] KEYS: trusted: Fix missing null return from kzalloc call

[Sumit Garg]

On Mon, 12 Apr 2021 at 21:31, Colin King <colin.king@canonical.com> wrote:
>
> From: Colin Ian King <colin.king@canonical.com>
>
> The kzalloc call can return null with the GFP_KERNEL flag so
> add a null check and exit via a new error exit label. Use the
> same exit error label for another error path too.
>
> Addresses-Coverity: ("Dereference null return value")
> Fixes: 830027e2cb55 ("KEYS: trusted: Add generic trusted keys framework")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  security/keys/trusted-keys/trusted_core.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>

Ah, it's my bad. Thanks for fixing this issue.

Reviewed-by: Sumit Garg <sumit.garg@linaro.org>

-Sumit

> diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
> index ec3a066a4b42..90774793f0b1 100644
> --- a/security/keys/trusted-keys/trusted_core.c
> +++ b/security/keys/trusted-keys/trusted_core.c
> @@ -116,11 +116,13 @@ static struct trusted_key_payload *trusted_payload_alloc(struct key *key)
>
>         ret = key_payload_reserve(key, sizeof(*p));
>         if (ret < 0)
> -               return p;
> +               goto err;
>         p = kzalloc(sizeof(*p), GFP_KERNEL);
> +       if (!p)
> +               goto err;
>
>         p->migratable = migratable;
> -
> +err:
>         return p;
>  }
>
> --
> 2.30.2
>

Re: [PATCH][next] KEYS: trusted: Fix missing null return from kzalloc call

[Jarkko Sakkinen]

On Mon, Apr 12, 2021 at 05:01:01PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The kzalloc call can return null with the GFP_KERNEL flag so
> add a null check and exit via a new error exit label. Use the
> same exit error label for another error path too.
> 
> Addresses-Coverity: ("Dereference null return value")
> Fixes: 830027e2cb55 ("KEYS: trusted: Add generic trusted keys framework")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
 
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

/Jarkko