From: Yonghong Song <yhs@fb.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Andrew Morton <akpm@linux-foundation.org>, <x86@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Masami Hiramatsu <mhiramat@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
<linux-parisc@vger.kernel.org>, <linux-um@lists.infradead.org>,
<netdev@vger.kernel.org>, <bpf@vger.kernel.org>,
<linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 12/23] bpf: handle the compat string in bpf_trace_copy_string better
Date: Thu, 28 May 2020 10:06:17 -0700 [thread overview]
Message-ID: <a1aa26f4-8c0a-5f8a-8460-6d61f167702d@fb.com> (raw)
In-Reply-To: <20200528043957.GA28494@lst.de>
On 5/27/20 9:39 PM, Christoph Hellwig wrote:
> On Wed, May 27, 2020 at 07:26:30PM -0700, Yonghong Song wrote:
>>> --- a/kernel/trace/bpf_trace.c~xxx
>>> +++ a/kernel/trace/bpf_trace.c
>>> @@ -588,15 +588,22 @@ BPF_CALL_5(bpf_seq_printf, struct seq_fi
>>> }
>>> if (fmt[i] == 's') {
>>> + void *unsafe_ptr;
>>> +
>>> /* try our best to copy */
>>> if (memcpy_cnt >= MAX_SEQ_PRINTF_MAX_MEMCPY) {
>>> err = -E2BIG;
>>> goto out;
>>> }
>>> - err = strncpy_from_unsafe(bufs->buf[memcpy_cnt],
>>> - (void *) (long) args[fmt_cnt],
>>> - MAX_SEQ_PRINTF_STR_LEN);
>>> + unsafe_ptr = (void *)(long)args[fmt_cnt];
>>> + if ((unsigned long)unsafe_ptr < TASK_SIZE) {
>>> + err = strncpy_from_user_nofault(
>>> + bufs->buf[memcpy_cnt], unsafe_ptr,
>>> + MAX_SEQ_PRINTF_STR_LEN);
>>> + } else {
>>> + err = -EFAULT;
>>> + }
>>
>> This probably not right.
>> The pointer stored at args[fmt_cnt] is a kernel pointer,
>> but it could be an invalid address and we do not want to fault.
>> Not sure whether it exists or not, we should use
>> strncpy_from_kernel_nofault()?
>
> If you know it is a kernel pointer with this series it should be
> strncpy_from_kernel_nofault. But even before the series it should have
> been strncpy_from_unsafe_strict.
The use of strncpy_from_unsafe() mimics old bpf_trace_printk()
implementation which just changed to _strict version:
https://lkml.org/lkml/2020/5/18/1309
Agreed that we should change to strncpy_from_unsafe_strict().
I can submit a patch for this.
Thanks!
WARNING: multiple messages have this Message-ID (diff)
From: Yonghong Song <yhs@fb.com>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-parisc@vger.kernel.org,
Daniel Borkmann <daniel@iogearbox.net>,
netdev@vger.kernel.org, x86@kernel.org,
linux-um@lists.infradead.org, Alexei Starovoitov <ast@kernel.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Masami Hiramatsu <mhiramat@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
bpf@vger.kernel.org
Subject: Re: [PATCH 12/23] bpf: handle the compat string in bpf_trace_copy_string better
Date: Thu, 28 May 2020 10:06:17 -0700 [thread overview]
Message-ID: <a1aa26f4-8c0a-5f8a-8460-6d61f167702d@fb.com> (raw)
In-Reply-To: <20200528043957.GA28494@lst.de>
On 5/27/20 9:39 PM, Christoph Hellwig wrote:
> On Wed, May 27, 2020 at 07:26:30PM -0700, Yonghong Song wrote:
>>> --- a/kernel/trace/bpf_trace.c~xxx
>>> +++ a/kernel/trace/bpf_trace.c
>>> @@ -588,15 +588,22 @@ BPF_CALL_5(bpf_seq_printf, struct seq_fi
>>> }
>>> if (fmt[i] == 's') {
>>> + void *unsafe_ptr;
>>> +
>>> /* try our best to copy */
>>> if (memcpy_cnt >= MAX_SEQ_PRINTF_MAX_MEMCPY) {
>>> err = -E2BIG;
>>> goto out;
>>> }
>>> - err = strncpy_from_unsafe(bufs->buf[memcpy_cnt],
>>> - (void *) (long) args[fmt_cnt],
>>> - MAX_SEQ_PRINTF_STR_LEN);
>>> + unsafe_ptr = (void *)(long)args[fmt_cnt];
>>> + if ((unsigned long)unsafe_ptr < TASK_SIZE) {
>>> + err = strncpy_from_user_nofault(
>>> + bufs->buf[memcpy_cnt], unsafe_ptr,
>>> + MAX_SEQ_PRINTF_STR_LEN);
>>> + } else {
>>> + err = -EFAULT;
>>> + }
>>
>> This probably not right.
>> The pointer stored at args[fmt_cnt] is a kernel pointer,
>> but it could be an invalid address and we do not want to fault.
>> Not sure whether it exists or not, we should use
>> strncpy_from_kernel_nofault()?
>
> If you know it is a kernel pointer with this series it should be
> strncpy_from_kernel_nofault. But even before the series it should have
> been strncpy_from_unsafe_strict.
The use of strncpy_from_unsafe() mimics old bpf_trace_printk()
implementation which just changed to _strict version:
https://lkml.org/lkml/2020/5/18/1309
Agreed that we should change to strncpy_from_unsafe_strict().
I can submit a patch for this.
Thanks!
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next prev parent reply other threads:[~2020-05-28 17:07 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-21 15:22 clean up and streamline probe_kernel_* and friends v4 Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 01/23] maccess: unexport probe_kernel_write and probe_user_write Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 02/23] maccess: remove various unused weak aliases Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 03/23] maccess: remove duplicate kerneldoc comments Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 04/23] maccess: clarify " Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 05/23] maccess: update the top of file comment Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 06/23] maccess: rename strncpy_from_unsafe_user to strncpy_from_user_nofault Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 07/23] maccess: rename strncpy_from_unsafe_strict to strncpy_from_kernel_nofault Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 08/23] maccess: rename strnlen_unsafe_user to strnlen_user_nofault Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 09/23] maccess: remove probe_read_common and probe_write_common Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 10/23] maccess: unify the probe kernel arch hooks Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-28 0:55 ` Andrew Morton
2020-05-28 0:55 ` Andrew Morton
2020-05-21 15:22 ` [PATCH 11/23] bpf: factor out a bpf_trace_copy_string helper Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 22:10 ` Andrii Nakryiko
2020-05-21 22:10 ` Andrii Nakryiko
2020-05-21 22:10 ` Andrii Nakryiko
2020-05-21 15:22 ` [PATCH 12/23] bpf: handle the compat string in bpf_trace_copy_string better Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 22:10 ` Andrii Nakryiko
2020-05-21 22:10 ` Andrii Nakryiko
2020-05-21 22:10 ` Andrii Nakryiko
2020-05-28 2:04 ` Andrew Morton
2020-05-28 2:04 ` Andrew Morton
2020-05-28 2:26 ` Yonghong Song
2020-05-28 2:26 ` Yonghong Song
2020-05-28 4:39 ` Christoph Hellwig
2020-05-28 4:39 ` Christoph Hellwig
2020-05-28 17:06 ` Yonghong Song [this message]
2020-05-28 17:06 ` Yonghong Song
2020-05-21 15:22 ` [PATCH 13/23] bpf: rework the compat kernel probe handling Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 22:10 ` Andrii Nakryiko
2020-05-21 22:10 ` Andrii Nakryiko
2020-05-21 22:10 ` Andrii Nakryiko
2020-05-21 15:22 ` [PATCH 14/23] tracing/kprobes: handle mixed kernel/userspace probes better Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-22 0:04 ` Masami Hiramatsu
2020-05-22 0:04 ` Masami Hiramatsu
2020-05-21 15:22 ` [PATCH 15/23] maccess: remove strncpy_from_unsafe Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 16/23] maccess: always use strict semantics for probe_kernel_read Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 17/23] maccess: move user access routines together Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 18/23] maccess: allow architectures to provide kernel probing directly Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 19/23] x86: use non-set_fs based maccess routines Christoph Hellwig
2020-05-21 15:22 ` Christoph Hellwig
2020-05-21 15:22 ` [PATCH 20/23] maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault Christoph Hellwig
2020-05-21 15:22 ` [PATCH 20/23] maccess: rename probe_kernel_{read, write} to copy_{from, to}_kernel_nofault Christoph Hellwig
2020-05-21 15:22 ` [PATCH 21/23] maccess: rename probe_user_{read,write} to copy_{from,to}_user_nofault Christoph Hellwig
2020-05-21 15:22 ` [PATCH 21/23] maccess: rename probe_user_{read, write} to copy_{from, to}_user_nofault Christoph Hellwig
2020-05-21 15:23 ` [PATCH 22/23] maccess: rename probe_kernel_address to get_kernel_nofault Christoph Hellwig
2020-05-21 15:23 ` Christoph Hellwig
2020-05-21 15:23 ` [PATCH 23/23] maccess: return -ERANGE when copy_from_kernel_nofault_allowed fails Christoph Hellwig
2020-05-21 15:23 ` Christoph Hellwig
2020-05-21 18:03 ` clean up and streamline probe_kernel_* and friends v4 Linus Torvalds
2020-05-21 18:03 ` Linus Torvalds
2020-05-21 18:03 ` Linus Torvalds
2020-05-22 0:22 ` Masami Hiramatsu
2020-05-22 0:22 ` Masami Hiramatsu
2020-05-25 22:19 ` Andrew Morton
2020-05-25 22:19 ` Andrew Morton
2020-05-26 6:13 ` Christoph Hellwig
2020-05-26 6:13 ` Christoph Hellwig
2020-05-28 0:36 ` Andrew Morton
2020-05-28 0:36 ` Andrew Morton
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