From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from air.basealt.ru (air.basealt.ru [193.43.8.18]) (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 636602417D9; Tue, 21 Apr 2026 13:27:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.43.8.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776778026; cv=none; b=SVJrxB+V/5T4eUQspNCGymLD+liqvihpVgxh0w937rlGu71HB6SfJtCHLFohql2viRoTbBxOt4Me5kE5kC1LUMmRFNAzTZpKeQrcNCADkZ5EVK1bPUGwwoYrdsukkw6pHD4I08YfjYEjpnagH/OEjPs0PDsF1bC8YtJfA5gHSlw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776778026; c=relaxed/simple; bh=QjHbiCWr0l2/cGP1WHcqBGnDFCoxWMk7Lc/zBqoModE=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=co7JcwRblvMi9LfohucqHvwXpZWwQOU3VwSs34FigQmQTCfP40BQuQgsYP0et3F9yWNpdbN5lKWlj0gteIeikxHxselqd9fjdVZMBrl1W8CH571mrHsjoLWZryg87z0CjZrBlQ1k1Eb+JTbMYfGwVzdl6vpv2rAf7QF3wCEIPpw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=altlinux.org; spf=pass smtp.mailfrom=altlinux.org; arc=none smtp.client-ip=193.43.8.18 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=altlinux.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=altlinux.org Received: from altlinux.ipa.basealt.ru (unknown [193.43.11.2]) (Authenticated sender: kovalevvv) by air.basealt.ru (Postfix) with ESMTPSA id A4E7C23390; Tue, 21 Apr 2026 16:27:02 +0300 (MSK) From: Vasiliy Kovalev To: stable@vger.kernel.org Cc: "David S . Miller" , Willem de Bruijn , Cezar Bulinaru , netdev@vger.kernel.org, lvc-project@linuxtesting.org, kovalev@altlinux.org Subject: [PATCH 5.15.y] net: tap: NULL pointer derefence in dev_parse_header_protocol when skb->dev is null Date: Tue, 21 Apr 2026 16:27:02 +0300 Message-Id: <20260421132702.38588-1-kovalev@altlinux.org> X-Mailer: git-send-email 2.33.8 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Cezar Bulinaru commit 4f61f133f354853bc394ec7d6028adb9b02dd701 upstream. Fixes a NULL pointer derefence bug triggered from tap driver. When tap_get_user calls virtio_net_hdr_to_skb the skb->dev is null (in tap.c skb->dev is set after the call to virtio_net_hdr_to_skb) virtio_net_hdr_to_skb calls dev_parse_header_protocol which needs skb->dev field to be valid. The line that trigers the bug is in dev_parse_header_protocol (dev is at offset 0x10 from skb and is stored in RAX register) if (!dev->header_ops || !dev->header_ops->parse_protocol) 22e1: mov 0x10(%rbx),%rax 22e5: mov 0x230(%rax),%rax Setting skb->dev before the call in tap.c fixes the issue. BUG: kernel NULL pointer dereference, address: 0000000000000230 RIP: 0010:virtio_net_hdr_to_skb.constprop.0+0x335/0x410 [tap] Code: c0 0f 85 b7 fd ff ff eb d4 41 39 c6 77 cf 29 c6 48 89 df 44 01 f6 e8 7a 79 83 c1 48 85 c0 0f 85 d9 fd ff ff eb b7 48 8b 43 10 <48> 8b 80 30 02 00 00 48 85 c0 74 55 48 8b 40 28 48 85 c0 74 4c 48 RSP: 0018:ffffc90005c27c38 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888298f25300 RCX: 0000000000000010 RDX: 0000000000000005 RSI: ffffc90005c27cb6 RDI: ffff888298f25300 RBP: ffffc90005c27c80 R08: 00000000ffffffea R09: 00000000000007e8 R10: ffff88858ec77458 R11: 0000000000000000 R12: 0000000000000001 R13: 0000000000000014 R14: ffffc90005c27e08 R15: ffffc90005c27cb6 FS: 0000000000000000(0000) GS:ffff88858ec40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000230 CR3: 0000000281408006 CR4: 00000000003706e0 Call Trace: tap_get_user+0x3f1/0x540 [tap] tap_sendmsg+0x56/0x362 [tap] ? get_tx_bufs+0xc2/0x1e0 [vhost_net] handle_tx_copy+0x114/0x670 [vhost_net] handle_tx+0xb0/0xe0 [vhost_net] handle_tx_kick+0x15/0x20 [vhost_net] vhost_worker+0x7b/0xc0 [vhost] ? vhost_vring_call_reset+0x40/0x40 [vhost] kthread+0xfa/0x120 ? kthread_complete_and_exit+0x20/0x20 ret_from_fork+0x1f/0x30 Fixes: 924a9bc362a5 ("net: check if protocol extracted by virtio_net_hdr_set_proto is correct") Signed-off-by: Cezar Bulinaru Reviewed-by: Willem de Bruijn Signed-off-by: David S. Miller [ kovalev: bp to fix CVE-2022-50073 ] Signed-off-by: Vasiliy Kovalev --- drivers/net/tap.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) diff --git a/drivers/net/tap.c b/drivers/net/tap.c index 53eadd82f9b8..a08adca412b4 100644 --- a/drivers/net/tap.c +++ b/drivers/net/tap.c @@ -703,11 +703,22 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control, skb_reset_mac_header(skb); skb->protocol = eth_hdr(skb)->h_proto; + rcu_read_lock(); + tap = rcu_dereference(q->tap); + if (!tap) { + kfree_skb(skb); + rcu_read_unlock(); + return total_len; + } + skb->dev = tap->dev; + if (vnet_hdr_len) { err = virtio_net_hdr_to_skb(skb, &vnet_hdr, tap_is_little_endian(q)); - if (err) + if (err) { + rcu_read_unlock(); goto err_kfree; + } } skb_probe_transport_header(skb); @@ -717,8 +728,6 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control, vlan_get_protocol_and_depth(skb, skb->protocol, &depth) != 0) skb_set_network_header(skb, depth); - rcu_read_lock(); - tap = rcu_dereference(q->tap); /* copy skb_ubuf_info for callback when skb has no error */ if (zerocopy) { skb_zcopy_init(skb, msg_control); @@ -727,14 +736,8 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control, uarg->callback(NULL, uarg, false); } - if (tap) { - skb->dev = tap->dev; - dev_queue_xmit(skb); - } else { - kfree_skb(skb); - } + dev_queue_xmit(skb); rcu_read_unlock(); - return total_len; err_kfree: -- 2.50.1