CVE-2026-31422

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_flow: fix NULL pointer dereference on shared blocks flow_change() calls tcf_block_q() and dereferences q->handle to derive a default baseclass. Shared blocks leave block->q NULL, causing a NULL deref when a flow filter without a fully qualified baseclass is created on a shared block. Check tcf_block_shared() before accessing block->q and return -EINVAL for shared blocks. This avoids the null-deref shown below: ======================================================================= KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f] RIP: 0010:flow_change (net/sched/cls_flow.c:508) Call Trace: tc_new_tfilter (net/sched/cls_api.c:2432) rtnetlink_rcv_msg (net/core/rtnetlink.c:6980) [...] =======================================================================

References

• https://git.kernel.org/stable/c/1a280dd4bd1d616a01d6ffe0de284c907b555504
• https://git.kernel.org/stable/c/415ea0c973c754b9f375225807810eb9045f4293
• https://git.kernel.org/stable/c/4a09f72007201c9f667dc47f64517ec23eea65e5
• https://git.kernel.org/stable/c/9bf5fc36a43f7b8b5507c96e74fb81f1e8b4957e
• https://git.kernel.org/stable/c/a208c3e1232997e9317887294c20008dfcb75449