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Message-ID: <CAADnVQLT9nSEqprcX_hmTeAYGVA9cWupVEfvhnyPuzWwrGKHcQ@mail.gmail.com>
Date: Tue, 6 Sep 2022 11:45:27 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Roberto Sassu <roberto.sassu@...weicloud.com>
Cc: Kumar Kartikeya Dwivedi <memxor@...il.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>,
Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
Mykola Lysenko <mykolal@...com>,
David Howells <dhowells@...hat.com>,
Jarkko Sakkinen <jarkko@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>,
Paul Moore <paul@...l-moore.com>,
James Morris <jmorris@...ei.org>,
"Serge E . Hallyn" <serge@...lyn.com>,
Shuah Khan <shuah@...nel.org>, bpf <bpf@...r.kernel.org>,
keyrings@...r.kernel.org,
LSM List <linux-security-module@...r.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Daniel Müller <deso@...teo.net>,
Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH v16 06/12] bpf: Add bpf_lookup_*_key() and bpf_key_put() kfuncs
On Tue, Sep 6, 2022 at 1:01 AM Roberto Sassu
<roberto.sassu@...weicloud.com> wrote:
>
> > > +struct bpf_key *bpf_lookup_user_key(u32 serial, u64 flags)
> > > +{
> > > + key_ref_t key_ref;
> > > + struct bpf_key *bkey;
> > > +
> > > + if (flags & ~KEY_LOOKUP_ALL)
> > > + return NULL;
> > > +
> > > + /*
> > > + * Permission check is deferred until the key is used, as
> > > the
> > > + * intent of the caller is unknown here.
> > > + */
> > > + key_ref = lookup_user_key(serial, flags,
> > > KEY_DEFER_PERM_CHECK);
> > > + if (IS_ERR(key_ref))
> > > + return NULL;
> > > +
> > > + bkey = kmalloc(sizeof(*bkey), GFP_ATOMIC);
> >
> > Since this function (due to lookup_user_key) is sleepable, do we
> > really need GFP_ATOMIC here?
>
> Daniel suggested it for bpf_lookup_system_key(), so that the kfunc does
> not have to be sleepable.
Hold on. It has to be sleepable. Just take a look
at what lookup_user_key is doing inside.
> For symmetry, I did the same to
> bpf_lookup_user_key(). Will switch back to GFP_KERNEL.
>
> Thanks
>
> Roberto
>
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