Re: [PATCH v3] bpf: Set register type according to is_valid_access()

From: David Miller
Date: Tue Sep 27 2016 - 03:52:20 EST

From: Mickaël Salaün <mic@xxxxxxxxxxx>
Date: Sat, 24 Sep 2016 20:01:50 +0200

> This prevent future potential pointer leaks when an unprivileged eBPF
> program will read a pointer value from its context. Even if
> is_valid_access() returns a pointer type, the eBPF verifier replace it
> with UNKNOWN_VALUE. The register value that contains a kernel address is
> then allowed to leak. Moreover, this fix allows unprivileged eBPF
> programs to use functions with (legitimate) pointer arguments.
> Not an issue currently since reg_type is only set for PTR_TO_PACKET or
> PTR_TO_PACKET_END in XDP and TC programs that can only be loaded as
> privileged. For now, the only unprivileged eBPF program allowed is for
> socket filtering and all the types from its context are UNKNOWN_VALUE.
> However, this fix is important for future unprivileged eBPF programs
> which could use pointers in their context.
> Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx>

Applied to net-next, thanks.