passt, util: Close any open file that the parent might have leaked

If a parent accidentally or due to implementation reasons leaks any
open file, we don't want to have access to them, except for the file
passed via --fd, if any.

This is the case for Podman when Podman's parent leaks files into
Podman: it's not practical for Podman to close unrelated files before
starting pasta, as reported by Paul.

Use close_range(2) to close all open files except for standard streams
and the one from --fd.

Given that parts of conf() depend on other files to be already opened,
such as the epoll file descriptor, we can't easily defer this to a
more convenient point, where --fd was already parsed. Introduce a
minimal, duplicate version of --fd parsing to keep this simple.

As we need to check that the passed --fd option doesn't exceed
INT_MAX, because we'll parse it with strtol() but file descriptor
indices are signed ints (regardless of the arguments close_range()
take), extend the existing check in the actual --fd parsing in conf(),
also rejecting file descriptors numbers that match standard streams,
while at it.

Suggested-by: Paul Holzinger <pholzing@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Paul Holzinger <pholzing@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/isolation.h b/isolation.h
index 846b2af..80bb68d 100644
--- a/isolation.h
+++ b/isolation.h
@@ -7,7 +7,7 @@
 #ifndef ISOLATION_H
 #define ISOLATION_H
 
-void isolate_initial(void);
+void isolate_initial(int argc, char **argv);
 void isolate_user(uid_t uid, gid_t gid, bool use_userns, const char *userns,
 		  enum passt_modes mode);
 int isolate_prefork(const struct ctx *c);