From: John Fastabend <john.fastabend@gmail.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
starmiku1207184332@gmail.com
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
martin.lau@linux.dev, song@kernel.org, yhs@fb.com,
john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com,
haoluo@google.com, jolsa@kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org, baijiaju1990@outlook.com
Subject: Re: [PATCH v2] kernel: bpf: stackmap: fix a possible sleep-in-atomic bug in bpf_mmap_unlock_get_irq_work()
Date: Fri, 17 Mar 2023 11:14:37 -0700 [thread overview]
Message-ID: <6414ae0db3f69_984f8208cb@john.notmuch> (raw)
In-Reply-To: <20230317171636.ftelyp6ty7mgo4rt@dhcp-172-26-102-232.dhcp.thefacebook.com>
Alexei Starovoitov wrote:
> On Fri, Mar 17, 2023 at 03:52:27AM +0000, starmiku1207184332@gmail.com wrote:
> > context because of its possible sleep operation. However, mmap_read_unlock()
> > is unsafely called in a preempt disabled context when spin_lock() or
> > rcu_read_lock() has been called.
>
> Why is that unsafe?
> See __up_read(). It's doing preempt_disable().
Yep I didn't see the issue either that is why I asked for the stack trace. If
its a bug we would want a reproducer as well seems like it should be trivially
tested in selftests.
>
>
> > - if (irqs_disabled()) {
> > + if (in_atomic() || irqs_disabled()) {
>
> We cannot do this. It will significantly hurt stack traces with build_id.
next prev parent reply other threads:[~2023-03-17 18:14 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-17 3:52 [PATCH v2] kernel: bpf: stackmap: fix a possible sleep-in-atomic bug in bpf_mmap_unlock_get_irq_work() starmiku1207184332
2023-03-17 17:16 ` Alexei Starovoitov
2023-03-17 18:14 ` John Fastabend [this message]
[not found] ` <CALyQVayJaZ_s9yuL07ReZRmTT52ua7B+92CdYnLi9GiegpOKNw@mail.gmail.com>
2023-03-19 16:47 ` Alexei Starovoitov
[not found] ` <CALyQVazN_KTOhNVowuOV4FSr_zd5htCaBJ+xKgCDaL1LgVG50Q@mail.gmail.com>
2023-03-20 15:20 ` Alexei Starovoitov
[not found] ` <CALyQVawAZQ=K5RCnq0yz+g3fUT6vd5h15wMAeGXnDwdrZi87Qg@mail.gmail.com>
2023-03-22 22:30 ` Alexei Starovoitov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6414ae0db3f69_984f8208cb@john.notmuch \
--to=john.fastabend@gmail.com \
--cc=alexei.starovoitov@gmail.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=baijiaju1990@outlook.com \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=haoluo@google.com \
--cc=jolsa@kernel.org \
--cc=kpsingh@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=martin.lau@linux.dev \
--cc=sdf@google.com \
--cc=song@kernel.org \
--cc=starmiku1207184332@gmail.com \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox