CVE-2023-53831 in Linux
Riassunto
di VulDB • 29/06/2026
Based on the crash dump provided, here is an analysis of the issue.
### **Summary** The system has crashed (likely a Kernel Panic or Oops) in the IPv6 output path (`ip6_finish_output2`) while processing traffic through an **IPvlan interface**. The call trace indicates that the crash occurred during packet transmission after network filtering hooks were processed.
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### **Key Components in Call Trace** 1. **`ipvlan_xmit_mode_l3` / `ipvlan_queue_xmit`**: Traffic is being sent out via an IPvlan device configured in L3 mode (`mode=l3`). This is a virtual network interface type introduced to provide layer-3 isolation without requiring MACVLAN or VLAN tagging.
2. **`ip6_output` → `NF_HOOK_COND`**: The packet went through the Netfilter hooks (`NF_HOOK_COND`) before being handed off to IPv6 output functions. This suggests that a netfilter rule (e.g., iptables/ip6tables, nftables) may have modified or inspected the packet just before transmission.
3. **`ip6_finish_output2`**: The crash occurred in `net/ipv6/ip6_output.c:83`, specifically inside `ip6_finish_output2`. This function is responsible for finalizing IPv6 packets, including handling fragmentation and calling device-specific xmit functions.
4. **Softirq Context (`<IRQ>`)**: The crash happened in a softirq context (`net_tx_action` → `__do_softirq`), which is normal for network transmission paths but means the kernel was processing deferred work when it faulted.
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### **Possible Causes** 1. **Bug in IPvlan Driver**: There may be a bug in the `ipvlan_core.c` or `ipvlan_main.c` code, especially if this is an older kernel version where IPvlan support had known issues with L3 mode and Netfilter interactions.
2. **Netfilter/IPv6 Interaction Bug**: If you are using complex netfilter rules (e.g., connection tracking, NAT, or custom hooks), there might be a race condition or invalid memory access when the packet is modified just before `ip6_finish_output2`.
3. **Corrupted Packet/SKB Structure**: The crash could result from a malformed socket buffer (`sk_buff`) being passed to IPv6 output functions. This can happen if: - A previous driver/module corrupted the SKB. - There is a memory corruption issue elsewhere in the system (e.g., use-after-free, double free).
4. **Kernel Bug**: If you are running an older kernel version, this might be a known bug that has been fixed in newer releases. Check for patches related to `ipvlan` and `ip6_output`.
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### **Recommended Actions** 1. **Check Kernel Version**: Identify your current kernel version (`uname -r`). If it is outdated, consider upgrading to the latest stable release where IPvlan bugs may have been fixed.
2. **Review Netfilter Rules**: Temporarily disable complex netfilter rules (especially those affecting IPv6) and test if the crash persists. This helps isolate whether a specific rule triggers the issue.
3. **Enable Debugging Options**: - Enable `CONFIG_DEBUG_SLAB` or `SLUB_DEBUG_ON` to detect memory corruption. - Use `kdump`/`crash` tools to analyze the full core dump for more details (e.g., which register caused the fault, invalid pointer access).
4. **Check dmesg Logs**: Look for earlier warnings or errors in `dmesg | grep ipvlan` or `dmesg | grep IPv6` that might indicate a preceding issue leading to this crash.
5. **Reproduce with Minimal Configuration**: - Try reproducing the issue without IPvlan (use standard VLANs or bridges) to confirm if it is specific to IPvlan L3 mode. - Test with minimal netfilter rules enabled.
6. **Report Bug**: If this is a reproducible bug in your kernel version, report it to the Linux networking maintainers via [[email protected]](mailto:[email protected]) or file an issue on [kernel.org](https://bugzilla.kernel.org/).
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### **Conclusion** The crash is likely due to a bug in the interaction between IPvlan L3 mode, Netfilter hooks, and IPv6 output processing. Upgrading the kernel, simplifying netfilter rules, or enabling memory debugging options will help pinpoint the root cause.
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