From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailout1.hostsharing.net (mailout1.hostsharing.net [83.223.95.204]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2F36D3644A4; Tue, 23 Jun 2026 09:26:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=83.223.95.204 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782206779; cv=none; b=avtLKFp7rj1v3J0PR57vBc8FstUR+fwHGVkNM+uwnZlf/yQapzJVxYoAlpo3d/TE4bScRAQ4b51HSCcfSgatfMQXTtrrmKuBmRUzN+nJlVPFJ/Wtc1CyH0SDj4ksKvsYB8pTFmvqycCvrYhhQb99tIxTSwZqsEIgpd3IEqjU2Zs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782206779; c=relaxed/simple; bh=3G+s78ZGaE4w/7G+m2+1z/grM1j3s1Or94a6zPTLhgE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=D6wmKyUCzr9m+QKiYNcXOc+tU+6lyLuJZscK5W4GnX444d3/1eAaKupzeA8T5xOrwPRjwzYoAB9xBmFnw/whbPc2jlSrqGWbQePe+Dh46hZc4QeGlfTFDcnEqQKADMubc90l1v0ZixvagM038pA381dhL4j/dmxm/0I8kjB6NXM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=wunner.de; spf=pass smtp.mailfrom=wunner.de; arc=none smtp.client-ip=83.223.95.204 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=wunner.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=wunner.de Received: from h08.hostsharing.net (h08.hostsharing.net [IPv6:2a01:37:1000::53df:5f1c:0]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature ECDSA (secp384r1) server-digest SHA384 client-signature ECDSA (secp384r1) client-digest SHA384) (Client CN "*.hostsharing.net", Issuer "GlobalSign GCC R6 AlphaSSL CA 2025" (verified OK)) by mailout1.hostsharing.net (Postfix) with ESMTPS id AB164367; Tue, 23 Jun 2026 11:26:05 +0200 (CEST) Received: by h08.hostsharing.net (Postfix, from userid 100393) id A3B1A602090D; Tue, 23 Jun 2026 11:26:05 +0200 (CEST) Date: Tue, 23 Jun 2026 11:26:05 +0200 From: Lukas Wunner To: azraelxuemo Cc: linux-crypto@vger.kernel.org, herbert@gondor.apana.org.au, dhowells@redhat.com, Ignat Korchagin , Jarkko Sakkinen , keyrings@vger.kernel.org Subject: Re: [PATCH] KEYS: asymmetric: fix OOB read in KEYCTL_PKEY_DECRYPT on zero-length message Message-ID: References: <20260622025002.798934-1-xuemo@xuemo.com> Precedence: bulk X-Mailing-List: keyrings@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260622025002.798934-1-xuemo@xuemo.com> [cc += Ignat, Jarkko, keyrings; start of thread is here: https://lore.kernel.org/r/20260622025002.798934-1-xuemo@xuemo.com ] On Mon, Jun 22, 2026 at 02:50:02AM +0000, azraelxuemo wrote: > When ret is replaced with maxsize, the caller keyctl_pkey_e_d_s() > does copy_to_user(_out, out, ret) with ret = key_size (e.g. 256 > for RSA-2048) on a buffer allocated with kmalloc(params.out_len), > which can be as small as 1 byte. This reads key_size - out_len > bytes beyond the allocation. It would probably make sense to tighten security in keyctl_pkey_e_d_s() by using kzalloc() instead of kmalloc() and by capping the amount of data copied with min(ret, params.out_len). > Fixes: 63ba4d67594a ("KEYS: asymmetric: Use new crypto interface without scatterlists") > Signed-off-by: HanQuan Please add: Cc: stable@vger.kernel.org # v6.5+ You don't need to cc that address when submitting the patch, but including the tag in the commit message helps stable maintainers identify patches that need backporting. > +++ b/crypto/asymmetric_keys/public_key.c > @@ -358,7 +358,10 @@ static int software_key_eds_op(struct kernel_pkey_params *params, > BUG(); > } > > - if (!issig && ret == 0) > + /* Decrypt may legitimately return 0 (zero-length message); only > + * replace ret with maxsize for encrypt, which returns 0 on success. > + */ > + if (!issig && ret == 0 && params->op == kernel_pkey_encrypt) > ret = crypto_akcipher_maxsize(tfm); Given that out of 3 operations (encrypt, decrypt, sign), 2 already return the size, I think a better approach would be to let crypto_akcipher_sync_encrypt() return crypto_akcipher_maxsize() on success, i.e.: return crypto_akcipher_sync_prep(&data) ?: crypto_akcipher_sync_post(&data, - crypto_akcipher_encrypt(data.req)); + crypto_akcipher_encrypt(data.req)) ?: + crypto_akcipher_maxsize(tfm); and then remove the if-clause in software_key_eds_op() altogether which overwrites ret with the maxsize. Do you agree? Your patch wasn't cc'ed to all maintainers of this file. Please double-check that you've checked out Linus' current master when running scripts/get_maintainer.pl. Thanks, Lukas