From: Christoph Hellwig <hch@lst.de>
To: lkp@lists.01.org
Subject: Re: [fs] 36e2c7421f: kernel-selftests.splice.short_splice_read.sh.fail
Date: Sat, 19 Sep 2020 07:07:39 +0200 [thread overview]
Message-ID: <20200919050739.GA7038@lst.de> (raw)
In-Reply-To: <202009181443.C2179FB@keescook>
[-- Attachment #1: Type: text/plain, Size: 1008 bytes --]
On Fri, Sep 18, 2020 at 02:49:19PM -0700, Kees Cook wrote:
> In response to my recent bug fix for splice vs sysfs binary handler[1],
> I added splice testing for other pseudo filesystems[2], for which the
> test output is seen above.
>
> What is the final verdict on the "should splice have a fallback mode?"
> question[3]? Right now /proc and /sys reject splice attempts (which, as
> I mentioned in the thread, is fine by me, since it would have blocked
> the bug I had to fix from ever being exposed in the first place).
The verdict is: without a set_fs()-like mechanism that allows uaccess
routines to operate on kernel buffers, or even worse a
compat_alloc_user_space-like mechanism we can't have an entirely
generic fallback.
> Should I update the test to _expect_ that splice should fail?
I think so. We can updated individual file operations to support splice
where actually used applications except it (even when they shouldn't),
but I'd rather not do it just for a test case.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Kees Cook <keescook@chromium.org>
Cc: Christoph Hellwig <hch@lst.de>, Al Viro <viro@zeniv.linux.org.uk>,
LKML <linux-kernel@vger.kernel.org>,
lkp@lists.01.org, lkp@intel.com,
kernel test robot <rong.a.chen@intel.com>
Subject: Re: [fs] 36e2c7421f: kernel-selftests.splice.short_splice_read.sh.fail
Date: Sat, 19 Sep 2020 07:07:39 +0200 [thread overview]
Message-ID: <20200919050739.GA7038@lst.de> (raw)
In-Reply-To: <202009181443.C2179FB@keescook>
On Fri, Sep 18, 2020 at 02:49:19PM -0700, Kees Cook wrote:
> In response to my recent bug fix for splice vs sysfs binary handler[1],
> I added splice testing for other pseudo filesystems[2], for which the
> test output is seen above.
>
> What is the final verdict on the "should splice have a fallback mode?"
> question[3]? Right now /proc and /sys reject splice attempts (which, as
> I mentioned in the thread, is fine by me, since it would have blocked
> the bug I had to fix from ever being exposed in the first place).
The verdict is: without a set_fs()-like mechanism that allows uaccess
routines to operate on kernel buffers, or even worse a
compat_alloc_user_space-like mechanism we can't have an entirely
generic fallback.
> Should I update the test to _expect_ that splice should fail?
I think so. We can updated individual file operations to support splice
where actually used applications except it (even when they shouldn't),
but I'd rather not do it just for a test case.
next prev parent reply other threads:[~2020-09-19 5:07 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-17 1:25 [fs] 36e2c7421f: kernel-selftests.splice.short_splice_read.sh.fail kernel test robot
2020-09-17 1:25 ` kernel test robot
2020-09-18 21:49 ` Kees Cook
2020-09-18 21:49 ` Kees Cook
2020-09-19 5:07 ` Christoph Hellwig [this message]
2020-09-19 5:07 ` Christoph Hellwig
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