CVE-2024-47728bpf: Zero former ARG_PTR_TO_{LONG,INT} args in case of error

Official description

In the Linux kernel, the following vulnerability has been resolved: bpf: Zero former ARG_PTR_TO_{LONG,INT} args in case of error For all non-tracing helpers which formerly had ARG_PTR_TO_{LONG,INT} as input arguments, zero the value for the case of an error as otherwise it could leak memory. For tracing, it is not needed given CAP_PERFMON can already read all kernel memory anyway hence bpf_get_func_arg() and bpf_get_func_ret() is skipped in here. Also, the MTU helpers mtu_len pointer value is being written but also read. Technically, the MEM_UNINIT should not be there in order to always force init. Removing MEM_UNINIT needs more verifier rework though: MEM_UNINIT right now implies two things actually: i) write into memory, ii) memory does not have to be initialized. If we lift MEM_UNINIT, it then becomes: i) read into memory, ii) memory must be initialized. This means that for bpf_*_check_mtu() we're readding the issue we're trying to fix, that is, it would then be able to write back into things like .rodata BPF maps. Follow-up work will rework the MEM_UNINIT semantics such that the intent can be better expressed. For now just clear the *mtu_len on error path which can be lifted later again.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/8397bf78988f3ae9dbebb0200189a62a57264980
• https://git.kernel.org/stable/c/a634fa8e480ac2423f86311a602f6295df2c8ed0
• https://git.kernel.org/stable/c/599d15b6d03356a97bff7a76155c5604c42a2962
• https://git.kernel.org/stable/c/594a9f5a8d2de2573a856e506f77ba7dd2cefc6a
• https://git.kernel.org/stable/c/4b3786a6c5397dc220b1483d8e2f4867743e966f
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html