CVE-2026-72151tpm: tpm2-sessions: wait for async KPP completion in tpm_buf_append_salt

Official description

In the Linux kernel, the following vulnerability has been resolved: tpm: tpm2-sessions: wait for async KPP completion in tpm_buf_append_salt tpm_buf_append_salt() in drivers/char/tpm/tpm2-sessions.c calls crypto_kpp_generate_public_key() and crypto_kpp_compute_shared_secret() without installing a completion callback, discards both return values, and immediately frees the kpp_request via kpp_request_free(). When the resolved ecdh-nist-p256 KPP backend is asynchronous (atmel-ecc, HPRE, keembay-ocs), either operation returns -EINPROGRESS and the deferred completion worker dereferences the freed request. The path fires automatically from the hwrng_fillfn kernel thread via tpm_get_random -> tpm2_get_random -> tpm2_start_auth_session -> tpm_buf_append_salt on every entropy poll, without any userland action. Install crypto_req_done as the completion callback, wrap both KPP operations in crypto_wait_req(), and propagate errors to the caller. The wait is a no-op for synchronous backends.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/111e520efbe82b324bc42b1999b723c0619eea6d
• https://git.kernel.org/stable/c/934d1cd40e2893bf7a041b54f6afd1c008d7a21c
• https://git.kernel.org/stable/c/493333f167926c7adab8e7563e21ad71d8af84fa
• https://git.kernel.org/stable/c/73851a7c43dfa52d2ed9415889b33daf85da0ed9