CVE-2024-47728: bpf: Zero former ARG_PTR_TO_{LONG,INT} args in case of error
First published: Mon Oct 21 2024(Updated: )
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.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel | >=5.2<6.1.113 | |
| Linux Kernel | >=6.2<6.6.54 | |
| Linux Kernel | >=6.7<6.10.13 | |
| Linux Kernel | >=6.11<6.11.2 |
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Reference Links
- 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
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