netdev - Re: [PATCH v3] bpf: Set register type according to is_valid

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Date:   Tue, 27 Sep 2016 03:52:01 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     mic@...ikod.net
Cc:     linux-kernel@...r.kernel.org, ast@...nel.org, luto@...capital.net,
        daniel@...earbox.net, keescook@...omium.org, sargun@...gun.me,
        tj@...nel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v3] bpf: Set register type according to
 is_valid_access()

From: Mickaël Salaün <mic@...ikod.net>
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@...ikod.net>

Applied to net-next, thanks.