From: Stephen Smalley <stephen.smalley.work@gmail.com>
To: NeilBrown <neilb@suse.de>
Cc: selinux@vger.kernel.org, linux-nfs@vger.kernel.org,
chuck.lever@oracle.com, jlayton@kernel.org, paul@paul-moore.com,
omosnace@redhat.com, linux-security-module@vger.kernel.org
Subject: Re: [PATCH v3] nfsd: set security label during create operations
Date: Wed, 15 May 2024 10:52:01 -0400 [thread overview]
Message-ID: <CAEjxPJ6DTNY3p9MmdV0K1A7No7joczGTeOe26Q4wr6yujk9zKA@mail.gmail.com> (raw)
In-Reply-To: <171497439414.9775.6998904788791406674@noble.neil.brown.name>
On Mon, May 6, 2024 at 1:46 AM NeilBrown <neilb@suse.de> wrote:
>
> On Fri, 03 May 2024, Stephen Smalley wrote:
> > When security labeling is enabled, the client can pass a file security
> > label as part of a create operation for the new file, similar to mode
> > and other attributes. At present, the security label is received by nfsd
> > and passed down to nfsd_create_setattr(), but nfsd_setattr() is never
> > called and therefore the label is never set on the new file. This bug
> > may have been introduced on or around commit d6a97d3f589a ("NFSD:
> > add security label to struct nfsd_attrs"). Looking at nfsd_setattr()
> > I am uncertain as to whether the same issue presents for
> > file ACLs and therefore requires a similar fix for those.
> >
> > An alternative approach would be to introduce a new LSM hook to set the
> > "create SID" of the current task prior to the actual file creation, which
> > would atomically label the new inode at creation time. This would be better
> > for SELinux and a similar approach has been used previously
> > (see security_dentry_create_files_as) but perhaps not usable by other LSMs.
> >
> > Reproducer:
> > 1. Install a Linux distro with SELinux - Fedora is easiest
> > 2. git clone https://github.com/SELinuxProject/selinux-testsuite
> > 3. Install the requisite dependencies per selinux-testsuite/README.md
> > 4. Run something like the following script:
> > MOUNT=$HOME/selinux-testsuite
> > sudo systemctl start nfs-server
> > sudo exportfs -o rw,no_root_squash,security_label localhost:$MOUNT
> > sudo mkdir -p /mnt/selinux-testsuite
> > sudo mount -t nfs -o vers=4.2 localhost:$MOUNT /mnt/selinux-testsuite
> > pushd /mnt/selinux-testsuite/
> > sudo make -C policy load
> > pushd tests/filesystem
> > sudo runcon -t test_filesystem_t ./create_file -f trans_test_file \
> > -e test_filesystem_filetranscon_t -v
> > sudo rm -f trans_test_file
> > popd
> > sudo make -C policy unload
> > popd
> > sudo umount /mnt/selinux-testsuite
> > sudo exportfs -u localhost:$MOUNT
> > sudo rmdir /mnt/selinux-testsuite
> > sudo systemctl stop nfs-server
> >
> > Expected output:
> > <eliding noise from commands run prior to or after the test itself>
> > Process context:
> > unconfined_u:unconfined_r:test_filesystem_t:s0-s0:c0.c1023
> > Created file: trans_test_file
> > File context: unconfined_u:object_r:test_filesystem_filetranscon_t:s0
> > File context is correct
> >
> > Actual output:
> > <eliding noise from commands run prior to or after the test itself>
> > Process context:
> > unconfined_u:unconfined_r:test_filesystem_t:s0-s0:c0.c1023
> > Created file: trans_test_file
> > File context: system_u:object_r:test_file_t:s0
> > File context error, expected:
> > test_filesystem_filetranscon_t
> > got:
> > test_file_t
> >
> > Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
> > ---
> > v3 removes the erroneous and unnecessary change to NFSv2 and updates the
> > description to note the possible origin of the bug. I did not add a
> > Fixes tag however as I have not yet tried confirming that.
>
> I think this bug has always been present - since label support was
> added.
> Commit d6a97d3f589a ("NFSD: add security label to struct nfsd_attrs")
> should have fixed it, but was missing the extra test that you provide.
>
> So
> Fixes: 0c71b7ed5de8 ("nfsd: introduce file_cache_mutex")
> might be appropriate - it fixes the patch, though not a bug introduced
> by the patch.
>
> Thanks for this patch!
> Reviewed-by: NeilBrown <neilb@suse.de>
FWIW, I finally got around to testing Linux v5.14 and it did pass
these NFS tests so this was a regression. I haven't been able to
bisect yet.
next prev parent reply other threads:[~2024-05-15 14:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-03 13:09 [PATCH v3] nfsd: set security label during create operations Stephen Smalley
2024-05-03 17:31 ` Jeffrey Layton
2024-05-04 15:23 ` Chuck Lever
2024-05-06 5:46 ` NeilBrown
2024-05-06 16:31 ` Stephen Smalley
2024-05-08 6:54 ` NeilBrown
2024-05-15 14:52 ` Stephen Smalley [this message]
2024-05-16 17:29 ` Stephen Smalley
2024-05-22 17:29 ` Stephen Smalley
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAEjxPJ6DTNY3p9MmdV0K1A7No7joczGTeOe26Q4wr6yujk9zKA@mail.gmail.com \
--to=stephen.smalley.work@gmail.com \
--cc=chuck.lever@oracle.com \
--cc=jlayton@kernel.org \
--cc=linux-nfs@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=neilb@suse.de \
--cc=omosnace@redhat.com \
--cc=paul@paul-moore.com \
--cc=selinux@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).