From: Kees Cook <kees@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Vegard Nossum <vegard.nossum@oracle.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Allen Pais <apais@linux.microsoft.com>,
Roman Kisel <romank@linux.microsoft.com>,
Xiaoming Ni <nixiaoming@huawei.com>,
Vijay Nag <nagvijay@microsoft.com>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] coredump: Do not lock during 'comm' reporting
Date: Sat, 28 Sep 2024 14:51:06 -0700 [thread overview]
Message-ID: <202409281449.B228D0C1E7@keescook> (raw)
In-Reply-To: <20240928144636.d1964e6c6bb77c3e9123fc64@linux-foundation.org>
On Sat, Sep 28, 2024 at 02:46:36PM -0700, Andrew Morton wrote:
> On Sat, 28 Sep 2024 14:39:45 -0700 Kees Cook <kees@kernel.org> wrote:
>
> > On Sat, Sep 28, 2024 at 02:35:32PM -0700, Andrew Morton wrote:
> > > On Sat, 28 Sep 2024 14:08:31 -0700 Kees Cook <kees@kernel.org> wrote:
> > >
> > > > The 'comm' member will always be NUL terminated,
> > >
> > > Why is this? I thought this is only true if the caller holds task_lock()?
> >
> > Because it's always written with strscpy_pad(). The final byte will
> > always be NUL. (And this has been true for a very long time.)
>
> So why does __get_task_comm() need to take task_lock()?
That was to make sure we didn't end up with garbled results, but
discussions have determined that we don't care:
https://lore.kernel.org/all/20240828030321.20688-1-laoar.shao@gmail.com/
But just for safety's sake, I'll change this memcpy to:
memcpy_and_pad(comm, sizeof(comm), current->comm, sizeof(comm) - 1, 0);
--
Kees Cook
next prev parent reply other threads:[~2024-09-28 21:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-28 21:08 [PATCH] coredump: Do not lock during 'comm' reporting Kees Cook
2024-09-28 21:35 ` Andrew Morton
2024-09-28 21:39 ` Kees Cook
2024-09-28 21:46 ` Andrew Morton
2024-09-28 21:51 ` Kees Cook [this message]
2024-09-29 18:42 ` Vegard Nossum
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