netdev - Re: [PATCH bpf-next v3 04/18] bpf: Allow struct

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <73d244186bdb206c62c62879c11f8139c79dfac9.camel@gmail.com>
Date: Mon, 03 Feb 2025 21:58:28 -0800
From: Eduard Zingerman <eddyz87@...il.com>
To: Amery Hung <ameryhung@...il.com>, netdev@...r.kernel.org
Cc: bpf@...r.kernel.org, daniel@...earbox.net, andrii@...nel.org, 
	alexei.starovoitov@...il.com, martin.lau@...nel.org, kuba@...nel.org, 
	edumazet@...gle.com, xiyou.wangcong@...il.com, cong.wang@...edance.com, 
	jhs@...atatu.com, sinquersw@...il.com, toke@...hat.com, jiri@...nulli.us, 
	stfomichev@...il.com, ekarani.silvestre@....ufcg.edu.br,
 yangpeihao@...u.edu.cn, 	yepeilin.cs@...il.com, ming.lei@...hat.com,
 kernel-team@...a.com
Subject: Re: [PATCH bpf-next v3 04/18] bpf: Allow struct_ops prog to return
 referenced kptr

On Fri, 2025-01-31 at 11:28 -0800, Amery Hung wrote:
> From: Amery Hung <amery.hung@...edance.com>
> 
> Allow a struct_ops program to return a referenced kptr if the struct_ops
> operator's return type is a struct pointer. To make sure the returned
> pointer continues to be valid in the kernel, several constraints are
> required:
> 
> 1) The type of the pointer must matches the return type
> 2) The pointer originally comes from the kernel (not locally allocated)
> 3) The pointer is in its unmodified form
> 
> Implementation wise, a referenced kptr first needs to be allowed to _leak_
> in check_reference_leak() if it is in the return register. Then, in
> check_return_code(), constraints 1-3 are checked. During struct_ops
> registration, a check is also added to warn about operators with
> non-struct pointer return.
> 
> In addition, since the first user, Qdisc_ops::dequeue, allows a NULL
> pointer to be returned when there is no skb to be dequeued, we will allow
> a scalar value with value equals to NULL to be returned.
> 
> In the future when there is a struct_ops user that always expects a valid
> pointer to be returned from an operator, we may extend tagging to the
> return value. We can tell the verifier to only allow NULL pointer return
> if the return value is tagged with MAY_BE_NULL.
> 
> Signed-off-by: Amery Hung <amery.hung@...edance.com>
> ---

Acked-by: Eduard Zingerman <eddyz87@...il.com>

[...]