From: Yafang Shao <laoar.shao@gmail.com>
To: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
Petr Mladek <pmladek@suse.com>,
Peter Zijlstra <peterz@infradead.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Valentin Schneider <valentin.schneider@arm.com>,
Qiang Zhang <qiang.zhang@windriver.com>,
robdclark <robdclark@chromium.org>,
christian <christian@brauner.io>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
David Miller <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>, Martin Lau <kafai@fb.com>,
Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
john fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
dennis.dalessandro@cornelisnetworks.com,
mike.marciniszyn@cornelisnetworks.com, dledford@redhat.com,
jgg@ziepe.ca, linux-rdma@vger.kernel.org,
netdev <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
"linux-perf-use." <linux-perf-users@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, Linux MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel test robot <oliver.sang@intel.com>,
kbuild test robot <lkp@intel.com>,
Andrii Nakryiko <andrii.nakryiko@gmail.com>
Subject: Re: [PATCH v6 08/12] tools/bpf/bpftool/skeleton: make it adopt to task comm size change
Date: Tue, 26 Oct 2021 10:18:51 +0800 [thread overview]
Message-ID: <CALOAHbDPs-pbr5CnmuRv+b+CgMdEkzi4Yr2fSO9pKCE-chr3Yg@mail.gmail.com> (raw)
In-Reply-To: <202110251421.7056ACF84@keescook>
On Tue, Oct 26, 2021 at 5:24 AM Kees Cook <keescook@chromium.org> wrote:
>
> On Mon, Oct 25, 2021 at 08:33:11AM +0000, Yafang Shao wrote:
> > bpf_probe_read_kernel_str() will add a nul terminator to the dst, then
> > we don't care about if the dst size is big enough.
> >
> > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> > Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> > Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
> > Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Steven Rostedt <rostedt@goodmis.org>
> > Cc: Al Viro <viro@zeniv.linux.org.uk>
> > Cc: Kees Cook <keescook@chromium.org>
> > Cc: Petr Mladek <pmladek@suse.com>
>
> So, if we're ever going to copying these buffers out of the kernel (I
> don't know what the object lifetime here in bpf is for "e", etc), we
> should be zero-padding (as get_task_comm() does).
>
> Should this, instead, be using a bounce buffer?
The comment in bpf_probe_read_kernel_str_common() says
: /*
: * The strncpy_from_kernel_nofault() call will likely not fill the
: * entire buffer, but that's okay in this circumstance as we're probing
: * arbitrary memory anyway similar to bpf_probe_read_*() and might
: * as well probe the stack. Thus, memory is explicitly cleared
: * only in error case, so that improper users ignoring return
: * code altogether don't copy garbage; otherwise length of string
: * is returned that can be used for bpf_perf_event_output() et al.
: */
It seems that it doesn't matter if the buffer is filled as that is
probing arbitrary memory.
>
> get_task_comm(comm, task->group_leader);
This helper can't be used by the BPF programs, as it is not exported to BPF.
> bpf_probe_read_kernel_str(&e.comm, sizeof(e.comm), comm);
>
> -Kees
>
> > ---
> > tools/bpf/bpftool/skeleton/pid_iter.bpf.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
> > index d9b420972934..f70702fcb224 100644
> > --- a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
> > +++ b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
> > @@ -71,8 +71,8 @@ int iter(struct bpf_iter__task_file *ctx)
> >
> > e.pid = task->tgid;
> > e.id = get_obj_id(file->private_data, obj_type);
> > - bpf_probe_read_kernel(&e.comm, sizeof(e.comm),
> > - task->group_leader->comm);
> > + bpf_probe_read_kernel_str(&e.comm, sizeof(e.comm),
> > + task->group_leader->comm);
> > bpf_seq_write(ctx->meta->seq, &e, sizeof(e));
> >
> > return 0;
> > --
> > 2.17.1
> >
>
> --
> Kees Cook
--
Thanks
Yafang
next prev parent reply other threads:[~2021-10-26 2:19 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-25 8:33 [PATCH v6 00/12] extend task comm from 16 to 24 Yafang Shao
2021-10-25 8:33 ` [PATCH v6 01/12] fs/exec: make __set_task_comm always set a nul ternimated string Yafang Shao
2021-10-25 21:07 ` Kees Cook
2021-10-26 1:48 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 02/12] fs/exec: make __get_task_comm always get a nul terminated string Yafang Shao
2021-10-25 21:08 ` Kees Cook
2021-10-26 1:49 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 03/12] drivers/connector: make connector comm always nul ternimated Yafang Shao
2021-10-25 21:14 ` Kees Cook
2021-10-26 1:50 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 04/12] drivers/infiniband: make setup_ctxt always get a nul terminated task comm Yafang Shao
2021-10-25 18:20 ` Dennis Dalessandro
2021-10-25 21:16 ` Kees Cook
2021-10-26 1:52 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 05/12] elfcore: make prpsinfo " Yafang Shao
2021-10-25 21:18 ` Kees Cook
2021-10-26 1:56 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 06/12] samples/bpf/test_overhead_kprobe_kern: make it adopt to task comm size change Yafang Shao
2021-10-25 21:20 ` Kees Cook
2021-10-25 8:33 ` [PATCH v6 07/12] samples/bpf/offwaketime_kern: make sched_switch tracepoint args adopt to " Yafang Shao
2021-10-25 21:21 ` Kees Cook
2021-10-26 1:56 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 08/12] tools/bpf/bpftool/skeleton: make it adopt to task " Yafang Shao
2021-10-25 21:24 ` Kees Cook
2021-10-26 2:18 ` Yafang Shao [this message]
2021-10-26 13:12 ` Steven Rostedt
2021-10-26 13:55 ` Yafang Shao
2021-10-26 14:02 ` Yafang Shao
2021-10-26 16:09 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 09/12] tools/perf/test: make perf test " Yafang Shao
2021-10-25 21:26 ` Kees Cook
2021-10-25 8:33 ` [PATCH v6 10/12] tools/testing/selftests/bpf: make it " Yafang Shao
2021-10-25 21:29 ` Kees Cook
2021-10-26 2:21 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 11/12] sched.h: extend task comm from 16 to 24 Yafang Shao
2021-10-25 21:30 ` Kees Cook
2021-10-26 2:22 ` Yafang Shao
2021-10-25 8:33 ` [PATCH v6 12/12] kernel/kthread: show a warning if kthread's comm is truncated Yafang Shao
2021-10-25 21:35 ` Kees Cook
2021-10-26 2:23 ` Yafang Shao
2021-10-27 20:10 ` Petr Mladek
2021-10-28 1:42 ` Yafang Shao
2021-10-29 7:44 ` Yafang Shao
2021-10-25 18:10 ` [PATCH v6 00/12] extend task comm from 16 to 24 Alexei Starovoitov
2021-10-25 21:05 ` Steven Rostedt
2021-10-25 21:06 ` Kees Cook
2021-10-26 10:35 ` Petr Mladek
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