| Message ID | 20220209111456.3328420-1-christian.ehrhardt@canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | tools/virtiofsd: Add rseq syscall to the seccomp allowlist | expand |
* christian.ehrhardt@canonical.com (christian.ehrhardt@canonical.com) wrote: > From: Christian Ehrhardt <christian.ehrhardt@canonical.com> > > The virtiofsd currently crashes when used with glibc 2.35. > That is due to the rseq system call being added to every thread > creation [1][2]. > > [1]: https://www.efficios.com/blog/2019/02/08/linux-restartable-sequences/ > [2]: https://sourceware.org/pipermail/libc-alpha/2022-February/136040.html > > This happens not at daemon start, but when a guest connects > > /usr/lib/qemu/virtiofsd -f --socket-path=/tmp/testvfsd -o sandbox=chroot \ > -o source=/var/guests/j-virtiofs --socket-group=kvm > virtio_session_mount: Waiting for vhost-user socket connection... > # start ok, now guest will connect > virtio_session_mount: Received vhost-user socket connection > virtio_loop: Entry > fv_queue_set_started: qidx=0 started=1 > fv_queue_set_started: qidx=1 started=1 > Bad system call (core dumped) > > We have to put rseq on the seccomp allowlist to avoid that the daemon > is crashing in this case. > > Reported-by: Michael Hudson-Doyle <michael.hudson@canonical.com> > Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com> Thanks! I bet this is going to pop up in zillions of programs. Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > --- > tools/virtiofsd/passthrough_seccomp.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/tools/virtiofsd/passthrough_seccomp.c b/tools/virtiofsd/passthrough_seccomp.c > index a3ce9f898d..21b8f53bd9 100644 > --- a/tools/virtiofsd/passthrough_seccomp.c > +++ b/tools/virtiofsd/passthrough_seccomp.c > @@ -116,6 +116,9 @@ static const int syscall_allowlist[] = { > SCMP_SYS(write), > SCMP_SYS(writev), > SCMP_SYS(umask), > +#ifdef __NR_rseq > + SCMP_SYS(rseq), /* required since glibc 2.35 */ > +#endif > }; > > /* Syscalls used when --syslog is enabled */ > -- > 2.35.0 > >
On Wed, Feb 09, 2022 at 12:14:56PM +0100, christian.ehrhardt@canonical.com wrote: > From: Christian Ehrhardt <christian.ehrhardt@canonical.com> > > The virtiofsd currently crashes when used with glibc 2.35. > That is due to the rseq system call being added to every thread > creation [1][2]. > > [1]: https://www.efficios.com/blog/2019/02/08/linux-restartable-sequences/ > [2]: https://sourceware.org/pipermail/libc-alpha/2022-February/136040.html > > This happens not at daemon start, but when a guest connects > > /usr/lib/qemu/virtiofsd -f --socket-path=/tmp/testvfsd -o sandbox=chroot \ > -o source=/var/guests/j-virtiofs --socket-group=kvm > virtio_session_mount: Waiting for vhost-user socket connection... > # start ok, now guest will connect > virtio_session_mount: Received vhost-user socket connection > virtio_loop: Entry > fv_queue_set_started: qidx=0 started=1 > fv_queue_set_started: qidx=1 started=1 > Bad system call (core dumped) > > We have to put rseq on the seccomp allowlist to avoid that the daemon > is crashing in this case. > > Reported-by: Michael Hudson-Doyle <michael.hudson@canonical.com> > Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com> > --- > tools/virtiofsd/passthrough_seccomp.c | 3 +++ > 1 file changed, 3 insertions(+) Thanks, applied to my block tree: https://gitlab.com/stefanha/qemu/commits/block Stefan
diff --git a/tools/virtiofsd/passthrough_seccomp.c b/tools/virtiofsd/passthrough_seccomp.c index a3ce9f898d..21b8f53bd9 100644 --- a/tools/virtiofsd/passthrough_seccomp.c +++ b/tools/virtiofsd/passthrough_seccomp.c @@ -116,6 +116,9 @@ static const int syscall_allowlist[] = { SCMP_SYS(write), SCMP_SYS(writev), SCMP_SYS(umask), +#ifdef __NR_rseq + SCMP_SYS(rseq), /* required since glibc 2.35 */ +#endif }; /* Syscalls used when --syslog is enabled */