linux-kernel - Re: [fuse-devel] copy_file

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: <CAJfpegur9fUQ8MaOqrE-XrGUDK40+PGQeMZ+AzzpX6hNV_BKsw@mail.gmail.com>
Date: Mon, 4 Aug 2025 15:30:27 +0200
From: Miklos Szeredi <miklos@...redi.hu>
To: Florian Weimer <fweimer@...hat.com>
Cc: fuse-devel@...ts.sourceforge.net, linux-api@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [fuse-devel] copy_file_range return value on FUSE

On Mon, 4 Aug 2025 at 11:42, Florian Weimer via fuse-devel
<fuse-devel@...ts.sourceforge.net> wrote:
>
> The FUSE protocol uses struct fuse_write_out to convey the return value
> of copy_file_range, which is restricted to uint32_t.  But the
> copy_file_range interface supports a 64-bit copy operation.  Given that
> copy_file_range is expected to clone huge files, large copies are not
> unexpected, so this appears to be a real limitation.

That's a nasty oversight.  Fixing with a new FUSE_COPY_FILE_RANGE_64
op, fallback to the legacy FUSE_COPY_FILE_RANGE.

> There is another wrinkle: we'd need to check if the process runs in
> 32-bit compat mode, and reject size_t arguments larger than INT_MAX in
> this case (with EOVERFLOW presumably).  But perhaps this should be
> handled on the kernel side?  Currently, this doesn't seem to happen, and
> we can get copy_file_range results in the in-band error range.
> Applications have no way to disambiguate this.

That's not fuse specific, right?

Thanks,
Miklos