From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 4 Oct 2019 19:54:00 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20191004185400.GH2772@work-vm> References: <20191004110759.32665-1-misono.tomohiro@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191004110759.32665-1-misono.tomohiro@jp.fujitsu.com> Subject: Re: [Virtio-fs] [PATCH] virtiofsd: Add pread64() to seccomp list for posix_fallocate() List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Misono Tomohiro Cc: virtio-fs@redhat.com, qemu-devel@nongnu.org * Misono Tomohiro (misono.tomohiro@jp.fujitsu.com) wrote: > I test virtiofs with NFS 4.0 as backend and notice that fallocate > causes system hang (kernel: 5.4-rc1, qemu: virtio-fs-dev branch): > $ mount -t virtiofs myfs /mnt > $ dd if=/dev/urandom bs=1000 seek=1 count=1 of=/mnt/file > $ fallocate -l 2000 /mnt/file # system hang > > This is because: > 1. virtiofs supports fallocate syscall while NFS 4.0 does not. > 2. virtiofsd uses posix_fallocate() and it fallbacks to pread64()/ > pwrite64() sequence to reserve blocks if fallocate syscall is > not available. > 3. pread64() syscall is prohibited by seccomp and virtiofsd thread > is killed by SIGSYS. > > So, just add pread64() to seccomp white list to fix this problem. > > Signed-off-by: Misono Tomohiro Thanks, I've squashed this into our seccomp commit. (It'll be a little while before I push it out, I need to finish a tidyup I'm doing). Dave > --- > contrib/virtiofsd/seccomp.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/contrib/virtiofsd/seccomp.c b/contrib/virtiofsd/seccomp.c > index 93b679271d..88b61bca42 100644 > --- a/contrib/virtiofsd/seccomp.c > +++ b/contrib/virtiofsd/seccomp.c > @@ -61,6 +61,7 @@ static const int syscall_whitelist[] = { > SCMP_SYS(ppoll), > SCMP_SYS(prctl), /* TODO restrict to just PR_SET_NAME? */ > SCMP_SYS(preadv), > + SCMP_SYS(pread64), > SCMP_SYS(pwritev), > SCMP_SYS(pwrite64), > SCMP_SYS(read), > -- > 2.21.0 > > _______________________________________________ > Virtio-fs mailing list > Virtio-fs@redhat.com > https://www.redhat.com/mailman/listinfo/virtio-fs -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK