linux-kernel - Re: BUG: ib_mad ftrace event unsupported migration

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Y2J9lAqBvjjPUmJf@ziepe.ca>
Date:   Wed, 2 Nov 2022 11:24:20 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Leonid Ravich <leonid.ravich@...anetworks.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Yigal Korman <yigal.korman@...anetworks.com>,
        "linux-trace-kernel@...r.kernel.org" 
        <linux-trace-kernel@...r.kernel.org>,
        Leon Ravich <lravich@...il.com>
Subject: Re: BUG:  ib_mad ftrace event unsupported migration

On Wed, Nov 02, 2022 at 10:17:19AM -0400, Steven Rostedt wrote:
> On Wed, 2 Nov 2022 11:04:44 -0300
> Jason Gunthorpe <jgg@...pe.ca> wrote:
> 
> > So this tracepoint is just wrong, you can't call a sleepable function
> > from a tracepoint like that?
> > 
> > Presumably lockdep would/should warn about this?
> 
> Why didn't it trigger a "scheduling while atomic" bug? That should
> happen if you call a sleeping function while preemption is disabled. Or
> does this function explicitly enable preemption? Which nothing checks
> if you enable preemption while recording to the ring buffer. I guess we
> could add that check, but this is not something that commonly happens
> enough to bother.

No, it doesn't muck with preemption, it will have some sleeping lock,
eg mlx5_ib_query_pkey() does a memory allocation as the first thing

It seems like a bug that calling kmalloc(GFP_KERNEL)/might_sleep()
from within a tracepoint doesn't trigger a warning?

Jason