From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 23A4246EF65; Tue, 21 Jul 2026 19:16:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784661387; cv=none; b=eP07Q0mXXyFabmF2MKNnQ5QOt9vvhHxad6ZeuJL+RR8xdobT8XuRejquQB9q7VtxcF9sEwDxIbiyv57neh1AEXaha2yuxX5BDnM9shy6eqC22vf/tDMa9jb5z2S/tv/CxhIuEEKujfIj7+eOC40/Ew2/3F6dWwmbw9MJpV0KePU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784661387; c=relaxed/simple; bh=XHsuLtQP3rPW531rtMxYXThJ9mqkJJa7SYpNycjgu2k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=L4gCgHKxjQDdLV+Ny3goOVHaUFC2aoJvD8fw1pLcKA1JuEH6JE0BLYg31Vu06rwu7e5q318CuFjkfboxZaX6lQjasqHB0FatDyX0/csEYvyGYUR1h4eA0RLaEdK1l4XDJ7UtDYPE29XOI6w5ABmul+fMaIM4zxeO3nBxFIc5UFg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=tK5ckFY0; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="tK5ckFY0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8532B1F000E9; Tue, 21 Jul 2026 19:16:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784661386; bh=vTcZV8EFHoc+2zHj07W9laqAbofxr9zvm132oOsz6Ec=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=tK5ckFY0jGIsW7Ix7cbitD/7G5PMUmRRhOPY55oXmtd2yb4tWwiJgOH8DTf65SxuV xU+3k+bvDDJ/ztxR3bTrj46OomGSUAgWWOG2Ov95pFSXPyHDnFCDTgupgDK6n8nB15 USDfVEvPKqClhMIXHD7xAOtSNWIxW3HoPSVi8t6I= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Muhammet=20Kaan=20KILIN=C3=87?= , Sasha Levin Subject: [PATCH 6.12 0011/1276] crypto: algif_skcipher - force synchronous processing Date: Tue, 21 Jul 2026 17:07:34 +0200 Message-ID: <20260721152446.328006258@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152446.065700225@linuxfoundation.org> References: <20260721152446.065700225@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Muhammet Kaan KILINÇ The AIO/async path in skcipher_recvmsg() passes the socket-wide ctx->iv directly into the skcipher request. After io_submit() the socket lock is dropped and the request is processed asynchronously by a worker (e.g. cryptd), which dereferences ctx->iv only later. A concurrent sendmsg(ALG_SET_IV) on the same socket can overwrite ctx->iv inside this window, so the in-flight request runs under an attacker-controlled IV. For CTR and other stream modes this causes IV/keystream reuse and allows an unprivileged user to recover the plaintext of a concurrent operation. Snapshotting ctx->iv into per-request storage for the async path is not sufficient here. For ciphers with statesize == 0 - which includes cbc and ctr - skcipher_prepare_alg() installs skcipher_noimport()/ skcipher_noexport(), so ctx->state carries nothing and the MSG_MORE inter-chunk IV chaining is carried solely by the in-place req->iv writeback. A snapshot redirects that writeback into per-request memory that af_alg_free_resources() releases on completion, so AIO + MSG_MORE with cbc/ctr would silently produce wrong output. Writing the IV back from the completion callback instead is not possible either: that would require lock_sock() there, but the callback can run in softirq/atomic context, so it must not sleep. Make the operation synchronous instead. ctx->iv is then only ever dereferenced under the socket lock held by recvmsg(), which removes the race, and the req->iv writeback lands in ctx->iv as before, which keeps MSG_MORE chaining intact for statesize == 0 ciphers. The ctx->state import/export path is unchanged for ciphers that do have state. This is equivalent to the upstream resolution: commit fcc77d33a34c ("net: Remove support for AIO on sockets") removed the AIO socket path across net/ entirely, producing the same end state for this file - algif_skcipher never processes an AIO request asynchronously. After this patch, _skcipher_recvmsg() matches mainline's crypto/algif_skcipher.c as it stands today, including the same now-dead -EIOCBQUEUED check. This patch deviates from that commit deliberately: rather than removing AIO socket support tree-wide, which would be far too invasive for stable, it removes only the AIO branch in crypto/algif_skcipher.c. io_submit() now completes synchronously, which is valid for the AIO interface; AF_ALG async is rarely used in practice. The -EIOCBQUEUED check in skcipher_recvmsg() is now dead but harmless, and is left alone to keep the fix minimal. Fixes: e870456d8e7c ("crypto: algif_skcipher - overhaul memory management") Cc: Reported-by: Muhammet Kaan KILINÇ Signed-off-by: Muhammet Kaan KILINÇ Signed-off-by: Sasha Levin --- crypto/algif_skcipher.c | 75 +++++++++++++---------------------------- 1 file changed, 24 insertions(+), 51 deletions(-) diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c index ba0a17fd95aca2..35ebc3e0201b04 100644 --- a/crypto/algif_skcipher.c +++ b/crypto/algif_skcipher.c @@ -79,20 +79,6 @@ static int algif_skcipher_export(struct sock *sk, struct skcipher_request *req) return err; } -static void algif_skcipher_done(void *data, int err) -{ - struct af_alg_async_req *areq = data; - struct sock *sk = areq->sk; - - if (err) - goto out; - - err = algif_skcipher_export(sk, &areq->cra_u.skcipher_req); - -out: - af_alg_async_cb(data, err); -} - static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg, size_t ignored, int flags) { @@ -171,43 +157,30 @@ static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg, cflags |= CRYPTO_SKCIPHER_REQ_CONT; } - if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) { - /* AIO operation */ - sock_hold(sk); - areq->iocb = msg->msg_iocb; - - /* Remember output size that will be generated. */ - areq->outlen = len; - - skcipher_request_set_callback(&areq->cra_u.skcipher_req, - cflags | - CRYPTO_TFM_REQ_MAY_SLEEP, - algif_skcipher_done, areq); - err = ctx->enc ? - crypto_skcipher_encrypt(&areq->cra_u.skcipher_req) : - crypto_skcipher_decrypt(&areq->cra_u.skcipher_req); - - /* AIO operation in progress */ - if (err == -EINPROGRESS) - return -EIOCBQUEUED; - - sock_put(sk); - } else { - /* Synchronous operation */ - skcipher_request_set_callback(&areq->cra_u.skcipher_req, - cflags | - CRYPTO_TFM_REQ_MAY_SLEEP | - CRYPTO_TFM_REQ_MAY_BACKLOG, - crypto_req_done, &ctx->wait); - err = crypto_wait_req(ctx->enc ? - crypto_skcipher_encrypt(&areq->cra_u.skcipher_req) : - crypto_skcipher_decrypt(&areq->cra_u.skcipher_req), - &ctx->wait); - - if (!err) - err = algif_skcipher_export( - sk, &areq->cra_u.skcipher_req); - } + /* + * Force synchronous processing. The async (AIO) path passed the + * socket-wide ctx->iv into the request, which the worker + * dereferenced after the socket lock had been dropped, letting a + * concurrent sendmsg(ALG_SET_IV) inject an attacker IV. Mainline + * removed the AIO socket path in commit fcc77d33a34c ("net: Remove + * support for AIO on sockets"); the minimal stable fix is to always + * complete synchronously, so ctx->iv is only ever dereferenced under + * the socket lock. This also keeps the IV chaining intact: for + * ciphers with statesize == 0 (e.g. ctr, cbc) the chained IV is + * carried by the req->iv writeback into ctx->iv, which is only + * consistent on the synchronous path. + */ + skcipher_request_set_callback(&areq->cra_u.skcipher_req, + cflags | + CRYPTO_TFM_REQ_MAY_SLEEP | + CRYPTO_TFM_REQ_MAY_BACKLOG, + crypto_req_done, &ctx->wait); + err = crypto_wait_req(ctx->enc ? + crypto_skcipher_encrypt(&areq->cra_u.skcipher_req) : + crypto_skcipher_decrypt(&areq->cra_u.skcipher_req), + &ctx->wait); + if (!err) + err = algif_skcipher_export(sk, &areq->cra_u.skcipher_req); free: af_alg_free_resources(areq); -- 2.53.0