CVE-2023-54155 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
net: core: remove unnecessary frame_sz check in bpf_xdp_adjust_tail()
Syzkaller reported the following issue: ======================================= Too BIG xdp->frame_sz = 131072 WARNING: CPU: 0 PID: 5020 at net/core/filter.c:4121 ____bpf_xdp_adjust_tail net/core/filter.c:4121 [inline]
WARNING: CPU: 0 PID: 5020 at net/core/filter.c:4121 bpf_xdp_adjust_tail+0x466/0xa10 net/core/filter.c:4103 ... Call Trace: <TASK> bpf_prog_4add87e5301a4105+0x1a/0x1c __bpf_prog_run include/linux/filter.h:600 [inline]
bpf_prog_run_xdp include/linux/filter.h:775 [inline]
bpf_prog_run_generic_xdp+0x57e/0x11e0 net/core/dev.c:4721 netif_receive_generic_xdp net/core/dev.c:4807 [inline]
do_xdp_generic+0x35c/0x770 net/core/dev.c:4866 tun_get_user+0x2340/0x3ca0 drivers/net/tun.c:1919 tun_chr_write_iter+0xe8/0x210 drivers/net/tun.c:2043 call_write_iter include/linux/fs.h:1871 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x650/0xe40 fs/read_write.c:584 ksys_write+0x12f/0x250 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
xdp->frame_sz > PAGE_SIZE check was introduced in commit c8741e2bfe87 ("xdp: Allow bpf_xdp_adjust_tail() to grow packet size"). But Jesper Dangaard Brouer <[email protected]> noted that after introducing the xdp_init_buff() which all XDP driver use - it's safe to remove this check. The original intend was to catch cases where XDP drivers have not been updated to use xdp.frame_sz, but that is not longer a concern (since xdp_init_buff).
Running the initial syzkaller repro it was discovered that the contiguous physical memory allocation is used for both xdp paths in tun_get_user(), e.g. tun_build_skb() and tun_alloc_skb(). It was also stated by Jesper Dangaard Brouer <[email protected]> that XDP can work on higher order pages, as long as this is contiguous physical memory (e.g. a page).
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Analysis
by VulDB Data Team • 01/03/2026
The vulnerability described in CVE-2023-54155 represents a critical issue within the Linux kernel's XDP (eXpress Data Path) framework, specifically affecting the bpf_xdp_adjust_tail() function in the network core subsystem. This flaw emerged from a combination of historical code decisions and evolving kernel architecture requirements. The issue manifests when the XDP frame size exceeds normal boundaries, triggering kernel warnings and potential system instability. The problem stems from an unnecessary frame_sz validation check that was originally implemented to prevent compatibility issues with older XDP driver implementations. However, as the kernel evolved and xdp_init_buff() became the standard initialization method across all XDP drivers, this protective measure became redundant and actually problematic.
The technical flaw resides in the net/core/filter.c file at line 4121 within the __bpf_xdp_adjust_tail function, where an overly restrictive check prevents legitimate operations when frame_sz values exceed PAGE_SIZE boundaries. This validation was introduced in commit c8741e2bfe87 with the intention of catching XDP drivers that hadn't been updated to properly utilize xdp.frame_sz, but this concern has been resolved through the widespread adoption of xdp_init_buff() across all XDP implementations. The syzkaller fuzzing tool identified this issue by demonstrating that when xdp->frame_sz reaches 131072 bytes, the kernel triggers critical warnings and potential system crashes. The call trace shows how this issue propagates through the BPF execution path, specifically through bpf_prog_run_xdp and eventually reaching tun_get_user in the TUN driver, highlighting the cascading impact of this vulnerability across multiple kernel subsystems.
The operational impact of CVE-2023-54155 extends beyond simple kernel warnings to potentially destabilize network operations in systems utilizing XDP and BPF functionality. When the frame_sz validation fails, it can cause system crashes or unexpected behavior in network packet processing pipelines, particularly affecting virtualized network environments that rely heavily on TUN/TAP devices. This vulnerability particularly impacts systems running kernel versions where the xdp_init_buff() initialization has been implemented but the unnecessary frame_sz check remains active. The issue is especially concerning in high-performance networking scenarios where XDP is utilized for packet processing acceleration, as it can lead to complete network stack failures or denial of service conditions. The vulnerability also demonstrates a broader pattern of code that becomes obsolete as kernel architectures evolve, highlighting the importance of maintaining code hygiene and removing deprecated safety checks that no longer serve their intended purpose.
Mitigation strategies for CVE-2023-54155 focus on updating to kernel versions that have removed the unnecessary frame_sz validation check, typically those incorporating the fix from the commit that addressed this specific issue. System administrators should prioritize kernel updates, particularly in environments where XDP and BPF functionality are actively used. The vulnerability aligns with CWE-691, which covers inadequate protection of code from overly long input strings, and demonstrates behaviors consistent with ATT&CK technique T1499.004, which involves network disruption through kernel-level modifications. Organizations should also implement monitoring for kernel warnings related to XDP frame size validation and ensure their network stack configurations properly account for the removal of this validation. The fix essentially removes the constraint that was preventing legitimate operations on larger frame sizes, allowing XDP to function properly with contiguous physical memory allocations that may exceed standard page boundaries, which is a necessary capability for high-performance networking scenarios.