CVE-2026-90393

Summary

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix potential UAF in bpf_netns_link_update_prog

In bpf_netns_link_update_prog, the checks for old_prog and prog type are currently performed locklessly before acquiring netns_bpf_mutex. This creates a race condition that can lead to a UAF issue.

If two threads concurrently execute BPF_LINK_UPDATE on the same netns link, the following execution path can trigger a UAF:

CPU0 CPU1 bpf_netns_link_update_prog if (old_prog && old_prog != link->prog) return -EPERM; bpf_netns_link_update_prog if (old_prog && old_prog != link->prog) … old_prog = xchg(&link->prog, new_prog); bpf_prog_put(old_prog); if (new_prog->type != link->prog->type) <– trigger UAF

Fix this by moving the old_prog and prog->type checks inside the netns_bpf_mutex critical section. Meanwhile, use guard() to simplify lock management and avoid all the goto jumping.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/d462b5481d77ce7df8a5ff89a699386f00c9214d
• https://git.kernel.org/stable/c/bdddf3e1493ee973619c154a57071ce67f78598b
• https://git.kernel.org/stable/c/79a66fd997d4eecf17302d613194879eb32e0986
• https://git.kernel.org/stable/c/f4ce6803df4095777191d800bebc50219b615ca0
• https://git.kernel.org/stable/c/277168cb9d153ce8e9c3f9275670e32ae61b41d6
• https://git.kernel.org/stable/c/bda86e9f31b9a296b6e64a51c91dc776fc9f613e
• https://git.kernel.org/stable/c/923f559e95b89b33c7e1793b3d8f7f4ec9b2e4b7
• https://git.kernel.org/stable/c/5c5997836381010fc5907b36bc17d3b19407e933

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