From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792509008; b=iF+bN95JK5InAD4QzyWczCk5nDQobuCfdgI2oxYzttEi77Zqv/bYsbZi6NwTvqpf5xwM mS3jL2bRy41cqfC9bCMWXoFmrZIUdlwp8z3As9uucO1HLfzzEyc+9Dk1EHDhAp3dPqOJs tHXB8PxnwOAlLPzvovii369UY5SQXZBbJKp4V6mlFe84W9WXsswJbrA2vLrP9qn6ToBG/ ZCbcRe6EnzicuhRtQBzWscGOItlzvDjs+WZhQwdO+/Q00888QY0enEsqNY0HCNX+5dHCr Pu69e2M5JkXYdSB7K6gNFy5xonFuonv/MtJ96askh/yXnQtNne6hoQx63yajGw9+crg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792509008; h=Received:Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; bh=Laxh79qXwAwsmuV6O1MzM4XcWCJ9HNwhZ1DgdfgCfZw=; b=bq+jY4h0zkd9OvIoq8eTjA2bcMNMRAI/qf95OO2/Vj6o2O0oyAhtHp7YrpmZ/t/gg1Lr Ncy82fPQGB9q/mVtdrMnBV4s3GEiFfE6/TBOJwu1BbDMFYt4TLg9o+4rx9YE5+KslzSvn EQivQgFAIFd8gPLobjZO2DEMykWwdKxdULb7AncvJfsPxFCG7GAUex1hSBUk/KJpexrfx phrJEesIhPdPFvF9sNBgMu/vbhK/NpZYmmBmHlHS5A/50jBfV7Q5FmfeGX3/ZxE0tFUwW nGpstLQhyD0P+9mrysTczncXH9/RxjnortyAu3M7BRsRepU7BNyWVnq50B4WCZF1V6g== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with UTF8SMTPS id 582CC606A31E; Tue, 20 Oct 2026 15:10:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with UTF8SMTPSA id 66F1B1F000C4; Tue, 20 Oct 2026 15:10:07 +0000 (UTC) Date: Tue, 20 Oct 2026 18:09:33 +0300 From: Jarkko Sakkinen To: Daehyeon Ko <4ncienth@gmail.com> Cc: James Bottomley , Mimi Zohar , linux-integrity@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KEYS: trusted: Reject short TPM2 public areas Message-ID: References: <20260925095308.3248297-1-4ncienth@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260925095308.3248297-1-4ncienth@gmail.com> On Fri, Sep 25, 2026 at 06:53:08PM +0900, Daehyeon Ko wrote: > tpm2_load_cmd() reads TPMA_OBJECT with get_unaligned_be32(pub + 4), but > does not require public_len to cover that field. > > A new-format blob with public_len zero makes the read begin at the end of New-format is not anything. TPM2 protocol format might be better here (nit). > the B + 4-byte decoded allocation, causing a four-byte heap out-of-bounds > read before the TPM command is transmitted. This is reachable from an > unprivileged add_key() call when TPM trusted keys and a TPM2 device are > available. > > This affects v5.13-rc1 and later kernels built with CONFIG_TRUSTED_KEYS=y > and CONFIG_TRUSTED_KEYS_TPM=y when a TPM2 device is present. A KASAN run > as UID 1000 with no effective capabilities reported: > > BUG: KASAN: slab-out-of-bounds in tpm2_unseal_trusted > Read of size 4 at addr ffff888106273b48 by task exploit/160 > CPU: 1 UID: 1000 PID: 160 Comm: exploit > The buggy address belongs to the object at ffff888106273b40 > which belongs to the cache kmalloc-8 of size 8 > The buggy address is located 0 bytes to the right of > allocated 8-byte region [ffff888106273b40, ffff888106273b48) > > TPMT_PUBLIC starts with the two-byte type, two-byte nameAlg and four-byte > objectAttributes fields. Require public_len to cover all eight bytes before > reading the attributes. > > The exact input produced the KASAN read in 3/3 fresh boots. The fixed build > rejected it with -E2BIG and no KASAN report in 3/3 boots; valid new- and > old-format trusted-key loads continued to succeed. > > Fixes: e5fb5d2c5a03 ("security: keys: trusted: Make sealed key properly interoperable") > Cc: stable@vger.kernel.org > Assisted-by: LLM > Signed-off-by: Daehyeon Ko <4ncienth@gmail.com> > --- > Tested with QEMU tpm-tis and swtpm: vulnerable 3/3 KASAN reports, > fixed 3/3 clean -E2BIG rejections, with public_len 7/8 and new/old-format > controls passing. Stable 5.15+ requires 114f00d738f1 first; both patches > apply cleanly in that order. > > The source reproducer and full logs are available privately on request. > > security/keys/trusted-keys/trusted_tpm2.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c > index c2a69bcf381d7..b3109e0a924f5 100644 > --- a/security/keys/trusted-keys/trusted_tpm2.c > +++ b/security/keys/trusted-keys/trusted_tpm2.c > @@ -418,6 +418,8 @@ static int tpm2_load_cmd(struct tpm_chip *chip, > public_len = get_unaligned_be16(blob + 2 + private_len); > if (private_len + 2 + public_len + 2 > blob_len) > return -E2BIG; I was writing summary of the changes for my v7.4-rc1 PR but this does not look right. This would really need an explanation like: /* * Check that TPMT_PUBLIC fields type, nameAlg and objectAttributes are covered * in order to avoid out-of-bounds read. */ > + if (public_len < 8) > + return -E2BIG; Why would you pick -E2BIG as I guess here that is not the problem? Just checking before proposing anything. > > pub = blob + 2 + private_len + 2; > /* key attributes are always at offset 4 */ > > base-commit: 27d14d3b15d5691bcbf0683883a2ea12469edbea I'll drop this patch and postpone v7.4-rc1 at least one day so there is still time. Br, Jarkko