Re: [PATCH] crypto: asymmetric_keys: copy X.509 TBS for data signature algorithms

[Herbert Xu <herbert@gondor.apana.org.au>]

On Fri, Aug 21, 2026 at 07:25:03PM +0000, Jérémy Jean wrote:
> For signature algorithms operating on a message rather than a digest,
> x509_get_sig_params() points sig->m directly into cert->tbs.
> cert->tbs is the preparsed add_key() payload.  The syscall wipes and frees
> it on return, while the instantiated key retains public_key_signature.
> 
> A later KEYCTL_LINK into an asymmetric restricted keyring therefore passes
> a dangling message pointer to ML-DSA.  KASAN reports a slab-use-after-free
> in mldsa_verify(), with allocation and free provenance both leading to
> __do_sys_add_key().  Reuse is also an integrity issue: bytes occupying the
> freed object become the authenticated message instead of the certificate's
> own TBSCertificate.
> 
> Give the signature object its own copy of the TBS, as is already done for
> a precomputed digest, and release it through the existing m_free contract.
> 
> Fixes: f3eccecd782d ("pkcs7: Allow the signing algo to do whatever digestion it wants itself")
> Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
> Assisted-by: Codex:gpt-5
> ---
>  crypto/asymmetric_keys/x509_public_key.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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