linux-kernel - Re: [PATCH] crypto: asymmetric_keys: fix uninitialized pointers with free attr

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Message-ID: <CALrw=nH8z0p=nyM_S0BN0JfdUB8fQHvkH6AULD3qj6sPQ1qJig@mail.gmail.com>
Date: Tue, 11 Nov 2025 13:12:20 +0000
From: Ignat Korchagin <ignat@...udflare.com>
To: Ally Heev <allyheev@...il.com>
Cc: David Howells <dhowells@...hat.com>, Lukas Wunner <lukas@...ner.de>, 
	Herbert Xu <herbert@...dor.apana.org.au>, "David S. Miller" <davem@...emloft.net>, 
	keyrings@...r.kernel.org, linux-crypto@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Dan Carpenter <dan.carpenter@...aro.org>
Subject: Re: [PATCH] crypto: asymmetric_keys: fix uninitialized pointers with
 free attr

Hi,

On Wed, Nov 5, 2025 at 9:53 AM Ally Heev <allyheev@...il.com> wrote:
>
> Uninitialized pointers with `__free` attribute can cause undefined
> behaviour as the memory assigned(randomly) to the pointer is freed
> automatically when the pointer goes out of scope
>
> crypto/asymmetric_keys doesn't have any bugs related to this as of now,
> but, it is better to initialize and assign pointers with `__free` attr
> in one statement to ensure proper scope-based cleanup
>
> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> Closes: https://lore.kernel.org/all/aPiG_F5EBQUjZqsl@stanley.mountain/
> Signed-off-by: Ally Heev <allyheev@...il.com>
> ---
>  crypto/asymmetric_keys/x509_cert_parser.c | 11 +++++++----
>  crypto/asymmetric_keys/x509_public_key.c  | 14 ++++++++------
>  2 files changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/crypto/asymmetric_keys/x509_cert_parser.c b/crypto/asymmetric_keys/x509_cert_parser.c
> index 8df3fa60a44f80fbd71af17faeca2e92b6cc03ce..bfd2cb2a9d81e3c615dfd4fe6f41653869a8cbd6 100644
> --- a/crypto/asymmetric_keys/x509_cert_parser.c
> +++ b/crypto/asymmetric_keys/x509_cert_parser.c
> @@ -60,12 +60,12 @@ EXPORT_SYMBOL_GPL(x509_free_certificate);
>   */
>  struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
>  {
> -       struct x509_certificate *cert __free(x509_free_certificate);

Should this be just initialized to NULL instead of moving the declaration?

> -       struct x509_parse_context *ctx __free(kfree) = NULL;

This pointer seems initialized. Is there still a problem?

>         struct asymmetric_key_id *kid;
>         long ret;
>
> -       cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL);
> +       struct x509_certificate *cert __free(x509_free_certificate) = kzalloc(
> +               sizeof(struct x509_certificate), GFP_KERNEL);
> +
>         if (!cert)
>                 return ERR_PTR(-ENOMEM);
>         cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
> @@ -74,7 +74,10 @@ struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
>         cert->sig = kzalloc(sizeof(struct public_key_signature), GFP_KERNEL);
>         if (!cert->sig)
>                 return ERR_PTR(-ENOMEM);
> -       ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
> +
> +       struct x509_parse_context *ctx __free(kfree) = kzalloc(
> +               sizeof(struct x509_parse_context), GFP_KERNEL);
> +
>         if (!ctx)
>                 return ERR_PTR(-ENOMEM);
>
> diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
> index 8409d7d36cb4f3582e15f9ee4d25f302b3b29358..818c9ab5d63940ff62c21666fd549d3a1ff07e67 100644
> --- a/crypto/asymmetric_keys/x509_public_key.c
> +++ b/crypto/asymmetric_keys/x509_public_key.c
> @@ -148,13 +148,13 @@ int x509_check_for_self_signed(struct x509_certificate *cert)
>   */
>  static int x509_key_preparse(struct key_preparsed_payload *prep)
>  {
> -       struct x509_certificate *cert __free(x509_free_certificate);

And here: should we just initialize this to NULL?

> -       struct asymmetric_key_ids *kids __free(kfree) = NULL;
> -       char *p, *desc __free(kfree) = NULL;

Same here: these two pointers are initialized.

> +       char *p;
>         const char *q;
>         size_t srlen, sulen;
>
> -       cert = x509_cert_parse(prep->data, prep->datalen);
> +       struct x509_certificate *cert __free(x509_free_certificate) =
> +               x509_cert_parse(prep->data, prep->datalen);
> +
>         if (IS_ERR(cert))
>                 return PTR_ERR(cert);
>
> @@ -187,7 +187,7 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
>                 q = cert->raw_serial;
>         }
>
> -       desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
> +       char *desc __free(kfree) = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
>         if (!desc)
>                 return -ENOMEM;
>         p = memcpy(desc, cert->subject, sulen);
> @@ -197,7 +197,9 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
>         p = bin2hex(p, q, srlen);
>         *p = 0;
>
> -       kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
> +       struct asymmetric_key_ids *kids __free(kfree) = kmalloc(
> +               sizeof(struct asymmetric_key_ids), GFP_KERNEL);
> +
>         if (!kids)
>                 return -ENOMEM;
>         kids->id[0] = cert->id;
>
> ---
> base-commit: c9cfc122f03711a5124b4aafab3211cf4d35a2ac
> change-id: 20251105-aheev-uninitialized-free-attr-crypto-bc94ec1b2253
>
> Best regards,
> --
> Ally Heev <allyheev@...il.com>
>

Ignat