linux-kernel - Re: PROBLEM: Firmware loader fallback mechanism no longer works with sendfile

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Date:   Tue, 5 Jan 2021 07:36:58 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Siddharth Gupta <sidgup@...eaurora.org>
Cc:     mcgrof@...nel.org, rafael@...nel.org, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "psodagud@...eaurora.org" <psodagud@...eaurora.org>
Subject: Re: PROBLEM: Firmware loader fallback mechanism no longer works with
 sendfile

On Mon, Jan 04, 2021 at 02:43:45PM -0800, Siddharth Gupta wrote:
> Hi all,
> 
> With the introduction of the filesystem change "fs: don't allow splice
> read/write without explicit ops"[1] the fallback mechanism of the firmware
> loader[2] no longer works when using sendfile[3] from the userspace.

What userspace program are you using to load firmware?  Are you not
using the in-kernel firmware loader for some reason?

> Since the binary attributes don't support splice_{read,write} functions the
> calls to splice_{read,write} used the default kernel_{read,write} functions.
> With the above change this results in an -EINVAL return from
> do_splice_from[4].
> 
> This essentially means that sendfile will not work for any binary attribute
> in the sysfs.

Have you tried fixing this with a patch much like what we did for the
proc files that needed this?  If not, can you?

> [1]: https://github.com/torvalds/linux/commit/36e2c7421f02a22f71c9283e55fdb672a9eb58e7#diff-70c49af2ed5805fc1406ed6e6532d6a029ada1abd90cca6442711b9cecd4d523
> [2]: https://github.com/torvalds/linux/blob/master/drivers/base/firmware_loader/main.c#L831
> [3]: https://github.com/torvalds/linux/blob/master/fs/read_write.c#L1257
> [4]: https://github.com/torvalds/linux/blob/master/fs/splice.c#L753

kernel development is on git.kernel.org, not github :)

thanks,

greg k-h