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

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

bpf: Zero former ARGPTRTO{LONG,INT} args in case of error

For all non-tracing helpers which formerly had ARGPTRTO{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 CAPPERFMON can already read all kernel memory anyway hence bpfgetfuncarg() and bpfgetfuncret() is skipped in here.

Also, the MTU helpers mtulen pointer value is being written but also read. Technically, the MEMUNINIT should not be there in order to always force init. Removing MEMUNINIT needs more verifier rework though: MEMUNINIT right now implies two things actually: i) write into memory, ii) memory does not have to be initialized. If we lift MEMUNINIT, it then becomes: i) read into memory, ii) memory must be initialized. This means that for bpfcheckmtu() 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 MEMUNINIT semantics such that the intent can be better expressed. For now just clear the mtulen on error path which can be lifted later again.

— NVD

This CVE was automatically created from a reference found in an email or other text. If you are reading this, then this CVE entry is probably erroneous, since this text should be replaced by the official CVE description automatically.

— Launchpad