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bh=JtaU6XyqFP8NrLJA88HkSXJMVAjAdcRT0OOcexGICOs=; b=ejaobmaAlIKEmzGAihgNplVWwZK2PX6s/rf7/rqevWlmNvpP5q+lx7V0zxoKM0/2Jv3tay 1FohM9EdPSm6FtXKWBvip8Ml9C5ZJ6Da6Hg2vgAXntuq6g97Nz0scwi7FJq58G5sAikBK3 5TBb+gX6PmUAwFE6sSVlPvzUhry+AoA= X-MC-Unique: G4rBlAc3O-CIqbpyd23T0g-1 From: Stefan Hajnoczi To: qemu-devel@nongnu.org Subject: [PATCH for-5.1 3/3] virtiofsd: probe unshare(CLONE_FS) and print an error Date: Wed, 22 Jul 2020 14:02:06 +0100 Message-Id: <20200722130206.224898-4-stefanha@redhat.com> In-Reply-To: <20200722130206.224898-1-stefanha@redhat.com> References: <20200722130206.224898-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; 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charset="utf-8" An assertion failure is raised during request processing if unshare(CLONE_FS) fails. Implement a probe at startup so the problem can be detected right away. Unfortunately Docker/Moby does not include unshare in the seccomp.json list unless CAP_SYS_ADMIN is given. Other seccomp.json lists always include unshare (e.g. podman is unaffected): https://raw.githubusercontent.com/seccomp/containers-golang/master/seccomp.= json Use "docker run --security-opt seccomp=3Dpath/to/seccomp.json ..." if the default seccomp.json is missing unshare. Cc: Misono Tomohiro Signed-off-by: Stefan Hajnoczi --- tools/virtiofsd/fuse_virtio.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c index 3b6d16a041..ebeb352514 100644 --- a/tools/virtiofsd/fuse_virtio.c +++ b/tools/virtiofsd/fuse_virtio.c @@ -949,6 +949,19 @@ int virtio_session_mount(struct fuse_session *se) { int ret; =20 + /* + * Test that unshare(CLONE_FS) works. fv_queue_worker() will need it. = It's + * an unprivileged system call but some Docker/Moby versions are known= to + * reject it via seccomp when CAP_SYS_ADMIN is not given. + */ + ret =3D unshare(CLONE_FS); + if (ret =3D=3D -1 && errno =3D=3D EPERM) { + fuse_log(FUSE_LOG_ERR, "unshare(CLONE_FS) failed with EPERM. If " + "running in a container please check that the container " + "runtime seccomp policy allows unshare.\n"); + return -1; + } + ret =3D fv_create_listen_socket(se); if (ret < 0) { return ret; --=20 2.26.2