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Re: [PATCH] virtiofsd: Seccomp: Add 'send' for syslog
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH] virtiofsd: Seccomp: Add 'send' for syslog |
Date: |
Mon, 2 Nov 2020 18:30:52 +0000 |
User-agent: |
Mutt/1.14.6 (2020-07-11) |
* Daniel P. Berrangé (berrange@redhat.com) wrote:
> On Mon, Nov 02, 2020 at 03:07:50PM +0000, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > On ppc it looks like syslog ends up using 'send' rather than 'sendto'.
> >
> > Reference: https://github.com/kata-containers/kata-containers/issues/1050
> >
> > Reported-by: amulmek1@in.ibm.com
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> > tools/virtiofsd/passthrough_seccomp.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/tools/virtiofsd/passthrough_seccomp.c
> > b/tools/virtiofsd/passthrough_seccomp.c
> > index eb9af8265f..672fb72a31 100644
> > --- a/tools/virtiofsd/passthrough_seccomp.c
> > +++ b/tools/virtiofsd/passthrough_seccomp.c
> > @@ -118,6 +118,7 @@ static const int syscall_whitelist[] = {
> >
> > /* Syscalls used when --syslog is enabled */
> > static const int syscall_whitelist_syslog[] = {
> > + SCMP_SYS(send),
> > SCMP_SYS(sendto),
> > };
>
> With glibc, syslog() calls __send() which for Linux target is implemented
> as:
>
>
> ssize_t
> __libc_send (int fd, const void *buf, size_t len, int flags)
> {
> #ifdef __ASSUME_SEND_SYSCALL
> return SYSCALL_CANCEL (send, fd, buf, len, flags);
> #elif defined __ASSUME_SENDTO_SYSCALL
> return SYSCALL_CANCEL (sendto, fd, buf, len, flags, NULL, 0);
> #else
> return SOCKETCALL_CANCEL (send, fd, buf, len, flags);
> #endif
> }
>
> We can see those defines being referenced vary per architecture:
>
> $ git grep -E '__ASSUME_SEND(TO)?_SYSCALL' sysdeps/
> sysdeps/unix/sysv/linux/alpha/kernel-features.h:#define __ASSUME_SEND_SYSCALL
> 1
> sysdeps/unix/sysv/linux/arm/kernel-features.h:#define __ASSUME_SEND_SYSCALL
> 1
> sysdeps/unix/sysv/linux/hppa/kernel-features.h:#define __ASSUME_SEND_SYSCALL
> 1
> sysdeps/unix/sysv/linux/i386/kernel-features.h:# undef __ASSUME_SENDTO_SYSCALL
> sysdeps/unix/sysv/linux/ia64/kernel-features.h:#define __ASSUME_SEND_SYSCALL
> 1
> sysdeps/unix/sysv/linux/kernel-features.h:#define __ASSUME_SENDTO_SYSCALL
> 1
> sysdeps/unix/sysv/linux/m68k/kernel-features.h:# undef __ASSUME_SENDTO_SYSCALL
> sysdeps/unix/sysv/linux/microblaze/kernel-features.h:#define
> __ASSUME_SEND_SYSCALL 1
> sysdeps/unix/sysv/linux/mips/kernel-features.h:# define __ASSUME_SEND_SYSCALL
> 1
> sysdeps/unix/sysv/linux/powerpc/kernel-features.h:#define
> __ASSUME_SEND_SYSCALL 1
> sysdeps/unix/sysv/linux/s390/kernel-features.h:# undef __ASSUME_SENDTO_SYSCALL
> sysdeps/unix/sysv/linux/send.c:#ifdef __ASSUME_SEND_SYSCALL
> sysdeps/unix/sysv/linux/send.c:#elif defined __ASSUME_SENDTO_SYSCALL
> sysdeps/unix/sysv/linux/sendto.c:#ifdef __ASSUME_SENDTO_SYSCALL
> sysdeps/unix/sysv/linux/sh/kernel-features.h:#define __ASSUME_SEND_SYSCALL
> 1
> sysdeps/unix/sysv/linux/sparc/kernel-features.h:# undef
> __ASSUME_SENDTO_SYSCALL
>
>
> So the patch is correct, but the commit message could be updated becase
> this isn't specific to PPC. Any platform except x86, s490, m68k will
> use send() rather than sendto() based on what I see here.
>
> With any commit message update, you can add
>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Thanks, changed to:
On ppc, and some other archs, it looks like syslog ends up using 'send'
rather than 'sendto'.
Dave
>
>
> Regards,
> Daniel
> --
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>
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK