Re: [PATCH] tools/virtiofsd: Add rseq syscall to the seccomp allowlist

[Stefan Hajnoczi]

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

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