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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.