CVE-2023-54216 in Linux
Riassunto
di VulDB • 10/08/2026
Based on the kernel stack trace provided, here is an analysis of the issue:
### **Summary** This is a **kernel crash (Oops/Panic)** occurring in the Linux networking subsystem while trying to add or modify a traffic control (`tc`) filter using the `cls_flower` classifier. The crash happens during hardware offload setup for an Mellanox ConnectX NIC driver (`mlx5_core`).
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### **Key Components Involved** 1. **`cls_flower`**: A Linux Traffic Control (TC) flower classifier module used to match complex packet headers (L2-L4). 2. **`mlx5_core` / `mlx5e_is_uplink_rep`**: Mellanox ConnectX network driver, specifically handling hardware offload for uplink representors. 3. **`tc_setup_action.part.0+0x9f/0x3b0`**: The crash occurs inside the action setup routine within TC infrastructure.
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### **Stack Trace Analysis** The call flow is: ```text rtnetlink_rcv_msg ← User-space command (e.g., `tc filter add`) received via netlink → tc_new_tfilter ← Kernel processing new TC filter rule → fl_change ← cls_flower classifier change handler → fl_hw_replace_filter ← Attempting to offload the filter to hardware → tc_setup_cb_add ← Adding a callback for action setup → ? tc_setup_action.part.0+0x9f/0x3b0 ← **CRASH HERE** ```
The crash occurs in `tc_setup_action` (or its part) when the kernel tries to set up an action associated with the flower filter, likely triggering a hardware offload path via the Mellanox driver.
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### **Likely Causes** 1. **Bug in `mlx5_core` Driver**: The most probable cause is a bug in the Mellanox driver’s handling of TC actions during hardware offload. Specifically: - Invalid pointer dereference or null pointer access when setting up an action (e.g., mirroring, redirect, VLAN push/pop). - Race condition between software filter update and hardware offload completion. 2. **Invalid TC Action Configuration**: The user-space command may have specified an unsupported or malformed action for the specific NIC/driver version. For example: - Offloading a complex action chain that the driver doesn’t fully support. - Using actions like `police`, `sample`, or nested actions incorrectly with flower filters on this hardware. 3. **Kernel Bug in TC Infrastructure**: Less likely, but possible corruption in `tc_setup_cb_add` if callbacks are mismanaged (e.g., double-free, use-after-free).
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### **Troubleshooting Steps** 1. **Check Kernel and Driver Versions**: - Identify the exact kernel version (`uname -r`). - Check Mellanox driver version (`ethtool -i <interface>` or `modinfo mlx5_core`). - Search for known bugs in these versions related to `mlx5e_tc_setup_action` or `cls_flower`.
2. **Reproduce with Minimal Configuration**: Try adding a simple TC filter without complex actions: ```bash tc filter add dev <iface> protocol ip parent ffff: flower dst_ip 192.168.1.1 action drop ``` If this works, gradually add more complex actions (e.g., `mirred`, `vlan`) to isolate the problematic one.
3. **Disable Hardware Offload Temporarily**: Test if disabling offloading prevents the crash: ```bash ethtool -K <iface> tx-off on rx-off on hw-tc-offload off ``` If this stabilizes the system, it confirms a driver/hardware offload bug.
4. **Check dmesg for More Context**: Look at logs *before* and *after* the crash stack trace for: - KASAN (Kernel Address Sanitizer) reports if enabled. - Warnings about invalid TC actions or unsupported features. - Previous crashes related to `mlx5` or `tc`.
5. **Update Driver/Kernel**: If a known bug exists, update the Mellanox driver and/or kernel to a newer version where this issue is fixed.
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### **Workaround** If immediate stability is required: - Disable hardware TC offload for the affected interface(s): ```bash tc qdisc del dev <iface> root ethtool -K <iface> hw-tc-offload off ``` - Avoid using complex `cls_flower` actions that trigger this code
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