Re: [PATCH] seccomp.sh: Quote tr character ranges to prevent glob expansion

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Nov 04, 2025 at 06:01:49AM +0100, Stefano Brivio wrote:
> On Mon,  3 Nov 2025 13:08:34 +0100
> Laurent Vivier <lvivier@redhat.com> wrote:
> 
> > we use [a-z] and [A-Z] patterns with 'tr', but
> > if there are files with names matching these patterns they will be
> > replaced by the name of the file and seccomp.h will not be generated
> > correctly:
> > $ rm seccomp.h
> > $ touch a b
> > $ make
> > tr: extra operand '[A-Z]'
> > Try 'tr --help' for more information.
> > seccomp profile passt allows:  accept accept4 bind clock_gettime close connect epoll_ctl epoll_pwait epoll_wait exit_group
> >    fallocate fcntl fsync ftruncate getsockname getsockopt listen lseek read recvfrom recvmmsg recvmsg sendmmsg sendmsg sendto
> > ...
> > cc -Wall -Wextra -Wno-format-zero-length -Wformat-security -pedantic -std=c11 -D_XOPEN_SOURCE=700 -D_GNU_SOURCE -D_FORTIFY_SOURCE=2 -O2 -pie -fPIE -DPAGE_SIZE=4096 -DVERSION="2025_09_19.623dbf6-54-gf6b6118fcabd" -DDUAL_STACK_SOCKETS=1 -DHAS_GETRANDOM -fstack-protector-strong   arch.c arp.c checksum.c conf.c dhcp.c dhcpv6.c epoll_ctl.c flow.c fwd.c icmp.c igmp.c inany.c iov.c ip.c isolation.c lineread.c log.c mld.c ndp.c netlink.c migrate.c packet.c passt.c pasta.c pcap.c pif.c repair.c tap.c tcp.c tcp_buf.c tcp_splice.c tcp_vu.c udp.c udp_flow.c udp_vu.c util.c vhost_user.c virtio.c vu_common.c -o passt
> > In file included from isolation.c:83:
> > seccomp.h:11:45: error: 'AUDIT_ARCH_' undeclared here (not in a function); did you mean 'AUDIT_ARCH'?
> >    11 |         BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, AUDIT_ARCH_, 0, 80),
> >       |                                             ^~~~~~~~~~~
> > 
> > Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> > ---
> >  seccomp.sh | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/seccomp.sh b/seccomp.sh
> > index a7bc417b9f6b..ba92b29d9a29 100755
> > --- a/seccomp.sh
> > +++ b/seccomp.sh
> > @@ -22,7 +22,7 @@ IN="$@"
> >  [ -z "${ARCH}" ] && ARCH="$(uname -m)"
> >  [ -z "${CC}" ] && CC="cc"
> >  
> > -AUDIT_ARCH="AUDIT_ARCH_$(echo ${ARCH} | tr [a-z] [A-Z]             \
> > +AUDIT_ARCH="AUDIT_ARCH_$(echo ${ARCH} | tr '[a-z]' '[A-Z]'         \
> 
> Oops.
> 
> I wonder if this is a complete fix though, because in general I didn't
> care about possible expansions and I just assumed I set -f on the whole
> script, which I didn't for some reason. That is, it should be:
> 
> #!/bin/sh -euf
> 
> and if you run 'shellcheck seccomp.sh', you'll find many other places
> where I didn't care, so perhaps we really need that -f, but I didn't
> look into all those shellcheck reports.
> 
> And by the way of shellcheck and compatibility, this is still on my
> to-do list:
> 
>   https://github.com/chimera-linux/cports/pull/1483#issuecomment-2079007408
> 
> All in all, I can apply this, it fixes a bit and surely doesn't hurt.
> 
> Or we can (also?) add -f, but we need to make sure we don't rely on
> expansions. We should perhaps check / fix reasonable shellcheck reports
> and compatibility issues too.

I don't love that idea.  I hadn't even realised -f existed until right
now, so having an obscure global flag change behaviour everywhere
doesn't ideal for readability.  Plus, disabling globs removes the need
for _some_ escaping, but not all, so it just means there's now two
different sets of rules you'd need to apply about what must be
escaped.

> 
> Let me know if you think you might find time for any of that, or if I
> should just apply this for the moment.
> 
> -- 
> Stefano
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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