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Re: [Virtio-fs] [PATCH] virtiofsd: Add pread64() to seccomp list for pos
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Virtio-fs] [PATCH] virtiofsd: Add pread64() to seccomp list for posix_fallocate() |
Date: |
Fri, 4 Oct 2019 19:54:00 +0100 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
* Misono Tomohiro (address@hidden) 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 <address@hidden>
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
> address@hidden
> https://www.redhat.com/mailman/listinfo/virtio-fs
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK