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 0783336C5BB for ; Fri, 29 May 2026 23:20:59 +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=1780096860; cv=none; b=fELTRz8HQb914c5cTWxl1vuCfnivQoQLrdMhHAY0nsOPdD724gRUWo+99bx8PUhdDwTaDa4rA1dakC7YzNrZrHIJStzAPFlgpxyGWChaIB01jTpmB8jNkjCn3ZH5l++vv3+3HQB39/+LYAuF3SwvUMDis99hL6tZT6NymgA7E6Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780096860; c=relaxed/simple; bh=GYRG+/70GP/TkWAZUUgEMDbZSOtUaEw67M4mRFiXhTs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YXqkwofMK9dlRaDLr8K7f1tcEgjOXd0I04zxxlen4HUfzCWv6pe8MI8H4WAtHxOqq1IqGQMmpyrGbf9q/mvbd8N9F881REGhZTE99dad6wKvbAtOGAjKow15wXW8KkIxen8/G+OLg2A8UD1yFbbWdK4wS+gU2pMFmdHhVofDVEY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PxMJpoX2; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PxMJpoX2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D74C91F00893; Fri, 29 May 2026 23:20:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780096858; bh=+7gSUQVoYtpNQrCFvteHJqlQ5qpmy/ig0rxUbPIQP/A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=PxMJpoX2Ebxou3UYQkaPQ73IuJ4msHKYQy5ccqutye4IrjUeHQyebOFNcKWJTNOCO eaMDhvDKhYiyGWgkb3PS+cjwzLTxh2KcTJrFJQlfnyL+7AFTHBZFBuRCXBAHySlB0X m5Lvu5zstNAvH9I84IcnqyFmuAbld1S7nM104YTdEt0OozN+i5sngu6zFloltZbmVh qUWdkLYDUtHJOvoofzkRExTiiztdhPjC3fSG3e8j7r66Oe28JOjG6LJHt4yIEWBQRW fGpSlvEA20Tdzt48Sb9ymaabe/ltdkB0i4/04lbgaZ/56MRxzcNE/CxHVJ8NwF8AZj tjCsOjMyrjEIg== From: Sasha Levin To: stable@vger.kernel.org Cc: David Howells , Hyunwoo Kim , Simon Horman , Jiayuan Chen , linux-afs@lists.infradead.org, Jeffrey Altman , Marc Dionne , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.6.y 1/2] rxrpc: Fix DATA decrypt vs splice() by copying data to buffer in recvmsg Date: Fri, 29 May 2026 19:20:55 -0400 Message-ID: <20260529232056.1870836-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026052809-espresso-heftiness-bdb0@gregkh> References: <2026052809-espresso-heftiness-bdb0@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: David Howells [ Upstream commit d2bc90cf6c75cb96d2ce549be6c35efa3099d25b ] This improves the fix for CVE-2026-43500. Fix the pagecache corruption from in-place decryption of a DATA packet transmitted locally by splice() by getting rid of the packet sharing in the I/O thread and unconditionally extracting the packet content into a bounce buffer in which the buffer is decrypted. recvmsg() (or the kernel equivalent) then copies the data from the bounce buffer to the destination buffer. The sk_buff then remains unmodified. This has an additional advantage in that the packet is then arranged in the buffer with the correct alignment required for the crypto algorithms to process directly. The performance of the crypto does seem to be a little faster and, surprisingly, the unencrypted performance doesn't seem to change much - possibly due to removing complexity from the I/O thread. Yet another advantage is that the I/O thread doesn't have to copy packets which would slow down packet distribution, ACK generation, etc.. The buffer belongs to the call and is allocated initially at 2K, sufficiently large to hold a whole jumbo subpacket, but the buffer will be increased in size if needed. However, to take this work, MSG_PEEK may cause a later packet to be decrypted into the buffer, in which case the earlier one will need re-decrypting for a subsequent recvmsg(). Note that rx_pkt_offset may legitimately see 0 as a valid offset now, so switch to using USHRT_MAX to indicate an invalid offset. Note also that I would generally prefer to replace the buffers of the current sk_buff with a new kmalloc'd buffer of the right size, ditching the old data and frags as this makes the handling of MSG_PEEK easier and removes the re-decryption issue, but this looks like quite a complicated thing to achieve. skb_morph() looks half way to what I want, but I don't want to have to allocate a new sk_buff. Fixes: d0d5c0cd1e71 ("rxrpc: Use skb_unshare() rather than skb_cow_data()") Reported-by: Hyunwoo Kim Closes: https://lore.kernel.org/r/afKV2zGR6rrelPC7@v4bel/ Signed-off-by: David Howells cc: Simon Horman cc: Jiayuan Chen cc: linux-afs@lists.infradead.org Reviewed-by: Jeffrey Altman Tested-by: Marc Dionne Link: https://patch.msgid.link/20260515230516.2718212-3-dhowells@redhat.com Signed-off-by: Jakub Kicinski Stable-dep-of: 8bfab4b6ffc2 ("rxrpc: Fix RESPONSE packet verification to extract skb to a linear buffer") Signed-off-by: Sasha Levin --- net/rxrpc/ar-internal.h | 7 +++- net/rxrpc/call_event.c | 27 +------------ net/rxrpc/call_object.c | 2 + net/rxrpc/insecure.c | 3 -- net/rxrpc/recvmsg.c | 68 +++++++++++++++++++++++++------- net/rxrpc/rxkad.c | 86 +++++++++++++++-------------------------- 6 files changed, 96 insertions(+), 97 deletions(-) diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index 1db479f3d6d3c..f19bc76b6c389 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -202,8 +202,6 @@ struct rxrpc_skb_priv { struct { u16 offset; /* Offset of data */ u16 len; /* Length of data */ - u8 flags; -#define RXRPC_RX_VERIFIED 0x01 }; struct { rxrpc_seq_t first_ack; /* First packet in acks table */ @@ -677,6 +675,11 @@ struct rxrpc_call { /* Received data tracking */ struct sk_buff_head recvmsg_queue; /* Queue of packets ready for recvmsg() */ struct sk_buff_head rx_oos_queue; /* Queue of out of sequence packets */ + void *rx_dec_buffer; /* Decryption buffer */ + unsigned short rx_dec_bsize; /* rx_dec_buffer size */ + unsigned short rx_dec_offset; /* Decrypted packet data offset */ + unsigned short rx_dec_len; /* Decrypted packet data len */ + rxrpc_seq_t rx_dec_seq; /* Packet in decryption buffer */ rxrpc_seq_t rx_highest_seq; /* Higest sequence number received */ rxrpc_seq_t rx_consumed; /* Highest packet consumed */ diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c index 07b2d81145d62..0f78544d043be 100644 --- a/net/rxrpc/call_event.c +++ b/net/rxrpc/call_event.c @@ -456,31 +456,8 @@ bool rxrpc_input_call_event(struct rxrpc_call *call, struct sk_buff *skb) resend = true; } - if (skb) { - struct rxrpc_skb_priv *sp = rxrpc_skb(skb); - - if (sp->hdr.type == RXRPC_PACKET_TYPE_DATA && - sp->hdr.securityIndex != 0 && - (skb_cloned(skb) || - skb_has_frag_list(skb) || - skb_has_shared_frag(skb))) { - /* Unshare the packet so that it can be modified by - * in-place decryption. - */ - struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC); - - if (nskb) { - rxrpc_new_skb(nskb, rxrpc_skb_new_unshared); - rxrpc_input_call_packet(call, nskb); - rxrpc_free_skb(nskb, rxrpc_skb_put_input); - } else { - /* OOM - Drop the packet. */ - rxrpc_see_skb(skb, rxrpc_skb_see_unshare_nomem); - } - } else { - rxrpc_input_call_packet(call, skb); - } - } + if (skb) + rxrpc_input_call_packet(call, skb); rxrpc_transmit_some_data(call); diff --git a/net/rxrpc/call_object.c b/net/rxrpc/call_object.c index 42d8b0bada4a9..ede2fbc661135 100644 --- a/net/rxrpc/call_object.c +++ b/net/rxrpc/call_object.c @@ -163,6 +163,7 @@ struct rxrpc_call *rxrpc_alloc_call(struct rxrpc_sock *rx, gfp_t gfp, spin_lock_init(&call->tx_lock); refcount_set(&call->ref, 1); call->debug_id = debug_id; + call->rx_pkt_offset = USHRT_MAX; call->tx_total_len = -1; call->next_rx_timo = 20 * HZ; call->next_req_timo = 1 * HZ; @@ -540,6 +541,7 @@ static void rxrpc_cleanup_ring(struct rxrpc_call *call) { rxrpc_purge_queue(&call->recvmsg_queue); rxrpc_purge_queue(&call->rx_oos_queue); + kfree(call->rx_dec_buffer); } /* diff --git a/net/rxrpc/insecure.c b/net/rxrpc/insecure.c index 34353b6e584bc..84d1bbb0ede2d 100644 --- a/net/rxrpc/insecure.c +++ b/net/rxrpc/insecure.c @@ -32,9 +32,6 @@ static int none_secure_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb) static int none_verify_packet(struct rxrpc_call *call, struct sk_buff *skb) { - struct rxrpc_skb_priv *sp = rxrpc_skb(skb); - - sp->flags |= RXRPC_RX_VERIFIED; return 0; } diff --git a/net/rxrpc/recvmsg.c b/net/rxrpc/recvmsg.c index b6e524c065f00..99efe14eb0c91 100644 --- a/net/rxrpc/recvmsg.c +++ b/net/rxrpc/recvmsg.c @@ -143,15 +143,52 @@ static void rxrpc_rotate_rx_window(struct rxrpc_call *call) } /* - * Decrypt and verify a DATA packet. + * Decrypt and verify a DATA packet. The content of the packet is pulled out + * into a flat buffer rather than decrypting in place in the skbuff. This also + * has the advantage of aligning the buffer correctly for the crypto routines. + * + * We keep track of the sequence number of the packet currently decrypted into + * the buffer in ->rx_dec_seq. If MSG_PEEK is used and steps onto a new + * packet, subsequent recvmsg() calls will have to go back and re-decrypt the + * current packet. */ static int rxrpc_verify_data(struct rxrpc_call *call, struct sk_buff *skb) { struct rxrpc_skb_priv *sp = rxrpc_skb(skb); + int ret; + + if (sp->len > call->rx_dec_bsize) { + /* Make sure we can hold a 1412-byte jumbo subpacket and make + * sure that the buffer size is aligned to a crypto blocksize. + */ + size_t size = clamp(round_up(sp->len, 32), 2048, 65535); + void *buffer = krealloc(call->rx_dec_buffer, size, GFP_NOFS); + + if (!buffer) + return -ENOMEM; + call->rx_dec_buffer = buffer; + call->rx_dec_bsize = size; + } + + ret = -EFAULT; + if (skb_copy_bits(skb, sp->offset, call->rx_dec_buffer, sp->len) < 0) + goto err; - if (sp->flags & RXRPC_RX_VERIFIED) - return 0; - return call->security->verify_packet(call, skb); + call->rx_dec_offset = 0; + call->rx_dec_len = sp->len; + call->rx_dec_seq = sp->hdr.seq; + ret = call->security->verify_packet(call, skb); + if (ret < 0) + goto err; + return 0; + +err: + kfree(call->rx_dec_buffer); + call->rx_dec_buffer = NULL; + call->rx_dec_bsize = 0; + call->rx_dec_offset = 0; + call->rx_dec_len = 0; + return ret; } /* @@ -202,17 +239,22 @@ static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call, if (msg) sock_recv_timestamp(msg, sock->sk, skb); - if (rx_pkt_offset == 0) { + if (call->rx_dec_seq != sp->hdr.seq || + !call->rx_dec_buffer) { ret2 = rxrpc_verify_data(call, skb); trace_rxrpc_recvdata(call, rxrpc_recvmsg_next, seq, - sp->offset, sp->len, ret2); + call->rx_dec_offset, + call->rx_dec_len, ret2); if (ret2 < 0) { kdebug("verify = %d", ret2); ret = ret2; goto out; } - rx_pkt_offset = sp->offset; - rx_pkt_len = sp->len; + } + + if (rx_pkt_offset == USHRT_MAX) { + rx_pkt_offset = call->rx_dec_offset; + rx_pkt_len = call->rx_dec_len; } else { trace_rxrpc_recvdata(call, rxrpc_recvmsg_cont, seq, rx_pkt_offset, rx_pkt_len, 0); @@ -224,10 +266,10 @@ static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call, if (copy > remain) copy = remain; if (copy > 0) { - ret2 = skb_copy_datagram_iter(skb, rx_pkt_offset, iter, - copy); - if (ret2 < 0) { - ret = ret2; + ret2 = copy_to_iter(call->rx_dec_buffer + rx_pkt_offset, + copy, iter); + if (ret2 != copy) { + ret = -EFAULT; goto out; } @@ -248,7 +290,7 @@ static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call, /* The whole packet has been transferred. */ if (sp->hdr.flags & RXRPC_LAST_PACKET) ret = 1; - rx_pkt_offset = 0; + rx_pkt_offset = USHRT_MAX; rx_pkt_len = 0; skb = skb_peek_next(skb, &call->recvmsg_queue); diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c index e2119af552500..228abd30847a3 100644 --- a/net/rxrpc/rxkad.c +++ b/net/rxrpc/rxkad.c @@ -412,27 +412,25 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb, rxrpc_seq_t seq, struct skcipher_request *req) { - struct rxkad_level1_hdr sechdr; + struct rxkad_level1_hdr *sechdr; struct rxrpc_skb_priv *sp = rxrpc_skb(skb); struct rxrpc_crypt iv; - struct scatterlist sg[16]; - u32 data_size, buf; + struct scatterlist sg[1]; + void *data = call->rx_dec_buffer; + u32 len = sp->len, data_size, buf; u16 check; int ret; _enter(""); - if (sp->len < 8) + if (len < 8) return rxrpc_abort_eproto(call, skb, RXKADSEALEDINCON, rxkad_abort_1_short_header); /* Decrypt the skbuff in-place. TODO: We really want to decrypt * directly into the target buffer. */ - sg_init_table(sg, ARRAY_SIZE(sg)); - ret = skb_to_sgvec(skb, sg, sp->offset, 8); - if (unlikely(ret < 0)) - return ret; + sg_init_one(sg, data, len); /* start the decryption afresh */ memset(&iv, 0, sizeof(iv)); @@ -446,13 +444,11 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb, return ret; /* Extract the decrypted packet length */ - if (skb_copy_bits(skb, sp->offset, &sechdr, sizeof(sechdr)) < 0) - return rxrpc_abort_eproto(call, skb, RXKADDATALEN, - rxkad_abort_1_short_encdata); - sp->offset += sizeof(sechdr); - sp->len -= sizeof(sechdr); + sechdr = data; + call->rx_dec_offset = sizeof(*sechdr); + len -= sizeof(*sechdr); - buf = ntohl(sechdr.data_size); + buf = ntohl(sechdr->data_size); data_size = buf & 0xffff; check = buf >> 16; @@ -461,10 +457,10 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb, if (check != 0) return rxrpc_abort_eproto(call, skb, RXKADSEALEDINCON, rxkad_abort_1_short_check); - if (data_size > sp->len) + if (data_size > len) return rxrpc_abort_eproto(call, skb, RXKADDATALEN, rxkad_abort_1_short_data); - sp->len = data_size; + call->rx_dec_len = data_size; _leave(" = 0 [dlen=%x]", data_size); return 0; @@ -478,43 +474,28 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb, struct skcipher_request *req) { const struct rxrpc_key_token *token; - struct rxkad_level2_hdr sechdr; + struct rxkad_level2_hdr *sechdr; struct rxrpc_skb_priv *sp = rxrpc_skb(skb); struct rxrpc_crypt iv; - struct scatterlist _sg[4], *sg; - u32 data_size, buf; + struct scatterlist sg[1]; + void *data = call->rx_dec_buffer; + u32 len = sp->len, data_size, buf; u16 check; - int nsg, ret; + int ret; - _enter(",{%d}", sp->len); + _enter(",{%d}", len); - if (sp->len < 8) + if (len < 8) return rxrpc_abort_eproto(call, skb, RXKADSEALEDINCON, rxkad_abort_2_short_header); /* Don't let the crypto algo see a misaligned length. */ - sp->len = round_down(sp->len, 8); + len = round_down(len, 8); - /* Decrypt the skbuff in-place. TODO: We really want to decrypt - * directly into the target buffer. + /* Decrypt in place in the call's decryption buffer. TODO: We really + * want to decrypt directly into the target buffer. */ - sg = _sg; - nsg = skb_shinfo(skb)->nr_frags + 1; - if (nsg <= 4) { - nsg = 4; - } else { - sg = kmalloc_array(nsg, sizeof(*sg), GFP_NOIO); - if (!sg) - return -ENOMEM; - } - - sg_init_table(sg, nsg); - ret = skb_to_sgvec(skb, sg, sp->offset, sp->len); - if (unlikely(ret < 0)) { - if (sg != _sg) - kfree(sg); - return ret; - } + sg_init_one(sg, data, len); /* decrypt from the session key */ token = call->conn->key->payload.data[0]; @@ -522,11 +503,9 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb, skcipher_request_set_sync_tfm(req, call->conn->rxkad.cipher); skcipher_request_set_callback(req, 0, NULL, NULL); - skcipher_request_set_crypt(req, sg, sg, sp->len, iv.x); + skcipher_request_set_crypt(req, sg, sg, len, iv.x); ret = crypto_skcipher_decrypt(req); skcipher_request_zero(req); - if (sg != _sg) - kfree(sg); if (ret < 0) { if (ret == -ENOMEM) return ret; @@ -535,13 +514,11 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb, } /* Extract the decrypted packet length */ - if (skb_copy_bits(skb, sp->offset, &sechdr, sizeof(sechdr)) < 0) - return rxrpc_abort_eproto(call, skb, RXKADDATALEN, - rxkad_abort_2_short_len); - sp->offset += sizeof(sechdr); - sp->len -= sizeof(sechdr); + sechdr = data; + call->rx_dec_offset = sizeof(*sechdr); + len -= sizeof(*sechdr); - buf = ntohl(sechdr.data_size); + buf = ntohl(sechdr->data_size); data_size = buf & 0xffff; check = buf >> 16; @@ -551,17 +528,18 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb, return rxrpc_abort_eproto(call, skb, RXKADSEALEDINCON, rxkad_abort_2_short_check); - if (data_size > sp->len) + if (data_size > len) return rxrpc_abort_eproto(call, skb, RXKADDATALEN, rxkad_abort_2_short_data); - sp->len = data_size; + call->rx_dec_len = data_size; _leave(" = 0 [dlen=%x]", data_size); return 0; } /* - * Verify the security on a received packet and the subpackets therein. + * Verify the security on a received (sub)packet. If the packet needs + * modifying (e.g. decrypting), it must be copied. */ static int rxkad_verify_packet(struct rxrpc_call *call, struct sk_buff *skb) { -- 2.53.0