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Message-ID: <2025123022-CVE-2023-54206-1057@gregkh>
Date: Tue, 30 Dec 2025 13:13:36 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-54206: net/sched: flower: fix filter idr initialization

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

net/sched: flower: fix filter idr initialization

The cited commit moved idr initialization too early in fl_change() which
allows concurrent users to access the filter that is still being
initialized and is in inconsistent state, which, in turn, can cause NULL
pointer dereference [0]. Since there is no obvious way to fix the ordering
without reverting the whole cited commit, alternative approach taken to
first insert NULL pointer into idr in order to allocate the handle but
still cause fl_get() to return NULL and prevent concurrent users from
seeing the filter while providing miss-to-action infrastructure with valid
handle id early in fl_change().

[  152.434728] general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN
[  152.436163] KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
[  152.437269] CPU: 4 PID: 3877 Comm: tc Not tainted 6.3.0-rc4+ #5
[  152.438110] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[  152.439644] RIP: 0010:fl_dump_key+0x8b/0x1d10 [cls_flower]
[  152.440461] Code: 01 f2 02 f2 c7 40 08 04 f2 04 f2 c7 40 0c 04 f3 f3 f3 65 48 8b 04 25 28 00 00 00 48 89 84 24 00 01 00 00 48 89 c8 48 c1 e8 03 <0f> b6 04 10 84 c0 74 08 3c 03 0f 8e 98 19 00 00 8b 13 85 d2 74 57
[  152.442885] RSP: 0018:ffff88817a28f158 EFLAGS: 00010246
[  152.443851] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[  152.444826] RDX: dffffc0000000000 RSI: ffffffff8500ae80 RDI: ffff88810a987900
[  152.445791] RBP: ffff888179d88240 R08: ffff888179d8845c R09: ffff888179d88240
[  152.446780] R10: ffffed102f451e48 R11: 00000000fffffff2 R12: ffff88810a987900
[  152.447741] R13: ffffffff8500ae80 R14: ffff88810a987900 R15: ffff888149b3c738
[  152.448756] FS:  00007f5eb2a34800(0000) GS:ffff88881ec00000(0000) knlGS:0000000000000000
[  152.449888] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  152.450685] CR2: 000000000046ad19 CR3: 000000010b0bd006 CR4: 0000000000370ea0
[  152.451641] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  152.452628] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  152.453588] Call Trace:
[  152.454032]  <TASK>
[  152.454447]  ? netlink_sendmsg+0x7a1/0xcb0
[  152.455109]  ? sock_sendmsg+0xc5/0x190
[  152.455689]  ? ____sys_sendmsg+0x535/0x6b0
[  152.456320]  ? ___sys_sendmsg+0xeb/0x170
[  152.456916]  ? do_syscall_64+0x3d/0x90
[  152.457529]  ? entry_SYSCALL_64_after_hwframe+0x46/0xb0
[  152.458321]  ? ___sys_sendmsg+0xeb/0x170
[  152.458958]  ? __sys_sendmsg+0xb5/0x140
[  152.459564]  ? do_syscall_64+0x3d/0x90
[  152.460122]  ? entry_SYSCALL_64_after_hwframe+0x46/0xb0
[  152.460852]  ? fl_dump_key_options.part.0+0xea0/0xea0 [cls_flower]
[  152.461710]  ? _raw_spin_lock+0x7a/0xd0
[  152.462299]  ? _raw_read_lock_irq+0x30/0x30
[  152.462924]  ? nla_put+0x15e/0x1c0
[  152.463480]  fl_dump+0x228/0x650 [cls_flower]
[  152.464112]  ? fl_tmplt_dump+0x210/0x210 [cls_flower]
[  152.464854]  ? __kmem_cache_alloc_node+0x1a7/0x330
[  152.465592]  ? nla_put+0x15e/0x1c0
[  152.466160]  tcf_fill_node+0x515/0x9a0
[  152.466766]  ? tc_setup_offload_action+0xf0/0xf0
[  152.467463]  ? __alloc_skb+0x13c/0x2a0
[  152.468067]  ? __build_skb_around+0x330/0x330
[  152.468814]  ? fl_get+0x107/0x1a0 [cls_flower]
[  152.469503]  tc_del_tfilter+0x718/0x1330
[  152.470115]  ? is_bpf_text_address+0xa/0x20
[  152.470765]  ? tc_ctl_chain+0xee0/0xee0
[  152.471335]  ? __kernel_text_address+0xe/0x30
[  152.471948]  ? unwind_get_return_address+0x56/0xa0
[  152.472639]  ? __thaw_task+0x150/0x150
[  152.473218]  ? arch_stack_walk+0x98/0xf0
[  152.473839]  ? __stack_depot_save+0x35/0x4c0
[  152.474501]  ? stack_trace_save+0x91/0xc0
[  152.475119]  ? security_capable+0x51/0x90
[  152.475741]  rtnetlink_rcv_msg+0x2c1/0x9d0
[  152.476387]  ? rtnl_calcit.isra.0+0x2b0/0x2b0
[  152.477042]  ? __sys_sendmsg+0xb5/0x140
[  152.477664]  ? do_syscall_64+0x3d/0x90
[  152.478255]  ? entry_SYSCALL_64_after_hwframe+0x46/0xb0
[  152.479010]  ? __stack_depot_save+0x35/0x4c0
[  152.479679]  ? __stack_depot_save+0x35/0x4c0
[  152.480346]  netlink_rcv_skb+0x12c/0x360
[  152.480929]  ? rtnl_calcit.isra.0+0x2b0/0x2b0
[  152.481517]  ? do_syscall_64+0x3d/0x90
[  152.482061]  ? netlink_ack+0x1550/0x1550
[  152.482612]  ? rhashtable_walk_peek+0x170/0x170
[  152.483262]  ? kmem_cache_alloc_node+0x1af/0x390
[  152.483875]  ? _copy_from_iter+0x3d6/0xc70
[  152.484528]  netlink_unicast+0x553/0x790
[  152.485168]  ? netlink_attachskb+0x6a0/0x6a0
[  152.485848]  ? unwind_next_frame+0x11cc/0x1a10
[  152.486538]  ? arch_stack_walk+0x61/0xf0
[  152.487169]  netlink_sendmsg+0x7a1/0xcb0
[  152.487799]  ? netlink_unicast+0x790/0x790
[  152.488355]  ? iovec_from_user.part.0+0x4d/0x220
[  152.488990]  ? _raw_spin_lock+0x7a/0xd0
[  152.489598]  ? netlink_unicast+0x790/0x790
[  152.490236]  sock_sendmsg+0xc5/0x190
[  152.490796]  ____sys_sendmsg+0x535/0x6b0
[  152.491394]  ? import_iovec+0x7/0x10
[  152.491964]  ? kernel_sendmsg+0x30/0x30
[  152.492561]  ? __copy_msghdr+0x3c0/0x3c0
[  152.493160]  ? do_syscall_64+0x3d/0x90
[  152.493706]  ___sys_sendmsg+0xeb/0x170
[  152.494283]  ? may_open_dev+0xd0/0xd0
[  152.494858]  ? copy_msghdr_from_user+0x110/0x110
[  152.495541]  ? __handle_mm_fault+0x2678/0x4ad0
[  152.496205]  ? copy_page_range+0x2360/0x2360
[  152.496862]  ? __fget_light+0x57/0x520
[  152.497449]  ? mas_find+0x1c0/0x1c0
[  152.498026]  ? sockfd_lookup_light+0x1a/0x140
[  152.498703]  __sys_sendmsg+0xb5/0x140
[  152.499306]  ? __sys_sendmsg_sock+0x20/0x20
[  152.499951]  ? do_user_addr_fault+0x369/0xd80
[  152.500595]  do_syscall_64+0x3d/0x90
[  152.501185]  entry_SYSCALL_64_after_hwframe+0x46/0xb0
[  152.501917] RIP: 0033:0x7f5eb294f887
[  152.502494] Code: 0a 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b9 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 89 54 24 1c 48 89 74 24 10
[  152.505008] RSP: 002b:00007ffd2c708f78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
[  152.506152] RAX: ffffffffffffffda RBX: 00000000642d9472 RCX: 00007f5eb294f887
[  152.507134] RDX: 0000000000000000 RSI: 00007ffd2c708fe0 RDI: 0000000000000003
[  152.508113] RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
[  152.509119] R10: 00007f5eb2808708 R11: 0000000000000246 R12: 0000000000000001
[  152.510068] R13: 0000000000000000 R14: 00007ffd2c70d1b8 R15: 0000000000485400
[  152.511031]  </TASK>
[  152.511444] Modules linked in: cls_flower sch_ingress openvswitch nsh mlx5_vdpa vringh vhost_iotlb vdpa mlx5_ib mlx5_core rpcrdma rdma_ucm ib_iser libiscsi scsi_transport_iscsi ib_umad rdma_cm ib_ipoib iw_cm ib_cm ib_uverbs ib_core xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink xt_addrtype iptable_nat nf_nat br_netfilter overlay zram zsmalloc fuse [last unloaded: mlx5_core]
[  152.515720] ---[ end trace 0000000000000000 ]---

The Linux kernel CVE team has assigned CVE-2023-54206 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.3 with commit 08a0063df3aed8d76a4034279117db12dbc1050f and fixed in 6.3.3 with commit 253a3a324e0ebc2825de76a0f5f17b8383b2023d
	Issue introduced in 6.3 with commit 08a0063df3aed8d76a4034279117db12dbc1050f and fixed in 6.4 with commit dd4f6bbfa646f258e5bcdfac57a5c413d687f588

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2023-54206
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/sched/cls_flower.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/253a3a324e0ebc2825de76a0f5f17b8383b2023d
	https://git.kernel.org/stable/c/dd4f6bbfa646f258e5bcdfac57a5c413d687f588

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