CVE-2023-54262 (published 2025-12-30)
In the Linux kernel, the following vulnerability has been resolved:

net/mlx5e: Don't clone flow post action attributes second time

The code already clones post action attributes in
mlx5e_clone_flow_attr_for_post_act(). Creating another copy in
mlx5e_tc_post_act_add() is a erroneous leftover from original
implementation. Instead, assign handle->attribute to post_attr provided by
the caller. Note that cloning the attribute second time is not just
wasteful but also causes issues like second copy not being properly updated
in neigh update code which leads to following use-after-free:

Feb 21 09:02:00 c-237-177-40-045 kernel: BUG: KASAN: use-after-free in mlx5_cmd_set_fte+0x200d/0x24c0 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  kasan_report+0xbb/0x1a0
Feb 21 09:02:00 c-237-177-40-045 kernel:  kasan_save_stack+0x1e/0x40
Feb 21 09:02:00 c-237-177-40-045 kernel:  kasan_set_track+0x21/0x30
Feb 21 09:02:00 c-237-177-40-045 kernel:  __kasan_kmalloc+0x7a/0x90
Feb 21 09:02:00 c-237-177-40-045 kernel:  kasan_save_stack+0x1e/0x40
Feb 21 09:02:00 c-237-177-40-045 kernel:  kasan_set_track+0x21/0x30
Feb 21 09:02:00 c-237-177-40-045 kernel:  kasan_save_free_info+0x2a/0x40
Feb 21 09:02:00 c-237-177-40-045 kernel:  ____kasan_slab_free+0x11a/0x1b0
Feb 21 09:02:00 c-237-177-40-045 kernel: page dumped because: kasan: bad access detected
Feb 21 09:02:00 c-237-177-40-045 kernel: mlx5_core 0000:08:00.0: mlx5_cmd_out_err:803:(pid 8833): SET_FLOW_TABLE_ENTRY(0x936) op_mod(0x0) failed, status bad resource state(0x9), syndrome (0xf2ff71), err(-22)
Feb 21 09:02:00 c-237-177-40-045 kernel: mlx5_core 0000:08:00.0 enp8s0f0: Failed to add post action rule
Feb 21 09:02:00 c-237-177-40-045 kernel: mlx5_core 0000:08:00.0: mlx5e_tc_encap_flows_add:190:(pid 8833): Failed to update flow post acts, -22
Feb 21 09:02:00 c-237-177-40-045 kernel: Call Trace:
Feb 21 09:02:00 c-237-177-40-045 kernel:  <TASK>
Feb 21 09:02:00 c-237-177-40-045 kernel:  dump_stack_lvl+0x57/0x7d
Feb 21 09:02:00 c-237-177-40-045 kernel:  print_report+0x170/0x471
Feb 21 09:02:00 c-237-177-40-045 kernel:  ? mlx5_cmd_set_fte+0x200d/0x24c0 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  kasan_report+0xbb/0x1a0
Feb 21 09:02:00 c-237-177-40-045 kernel:  ? mlx5_cmd_set_fte+0x200d/0x24c0 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  mlx5_cmd_set_fte+0x200d/0x24c0 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  ? __module_address.part.0+0x62/0x200
Feb 21 09:02:00 c-237-177-40-045 kernel:  ? mlx5_cmd_stub_create_flow_table+0xd0/0xd0 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  ? __raw_spin_lock_init+0x3b/0x110
Feb 21 09:02:00 c-237-177-40-045 kernel:  mlx5_cmd_create_fte+0x80/0xb0 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  add_rule_fg+0xe80/0x19c0 [mlx5_core]
--
Feb 21 09:02:00 c-237-177-40-045 kernel: Allocated by task 13476:
Feb 21 09:02:00 c-237-177-40-045 kernel:  kasan_save_stack+0x1e/0x40
Feb 21 09:02:00 c-237-177-40-045 kernel:  kasan_set_track+0x21/0x30
Feb 21 09:02:00 c-237-177-40-045 kernel:  __kasan_kmalloc+0x7a/0x90
Feb 21 09:02:00 c-237-177-40-045 kernel:  mlx5_packet_reformat_alloc+0x7b/0x230 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  mlx5e_tc_tun_create_header_ipv4+0x977/0xf10 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  mlx5e_attach_encap+0x15b4/0x1e10 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  post_process_attr+0x305/0xa30 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  mlx5e_tc_add_fdb_flow+0x4c0/0xcf0 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  __mlx5e_add_fdb_flow+0x7cf/0xe90 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  mlx5e_configure_flower+0xcaa/0x4b90 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  mlx5e_rep_setup_tc_cls_flower+0x99/0x1b0 [mlx5_core]
Feb 21 09:02:00 c-237-177-40-045 kernel:  mlx5e_rep_setup_tc_cb+0x133/0x1e0 [mlx5_core]
--
Feb 21 09:02:00 c-237-177-40-045 kernel: Freed by task 8833:
Feb 21 09:02:00 c-237-177-40-045 kernel:  kasan_save_s
---truncated---
Severity: HIGH (CVSS 3.1 vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)