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.
Suggested-by: Paul Holzinger <pholzing(a)redhat.com>
Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>
---
conf.c | 1 +
passt.c | 2 ++
util.c | 36 ++++++++++++++++++++++++++++++++++++
util.h | 1 +
4 files changed, 40 insertions(+)
diff --git a/conf.c b/conf.c
index 14d8ece..89f5b3d 100644
--- a/conf.c
+++ b/conf.c
@@ -1260,6 +1260,7 @@ void conf(struct ctx *c, int argc, char **argv)
c->tcp.fwd_in.mode = c->tcp.fwd_out.mode = FWD_UNSET;
c->udp.fwd_in.mode = c->udp.fwd_out.mode = FWD_UNSET;
+ optind = 1;
do {
name = getopt_long(argc, argv, optstring, options, NULL);
diff --git a/passt.c b/passt.c
index ea5bece..be7e84a 100644
--- a/passt.c
+++ b/passt.c
@@ -211,6 +211,8 @@ int main(int argc, char **argv)
arch_avx2_exec(argv);
+ close_open_files(argc, argv);
+
isolate_initial();
c.pasta_netns_fd = c.fd_tap = c.pidfile_fd = -1;
diff --git a/util.c b/util.c
index 54a9f58..ca627c6 100644
--- a/util.c
+++ b/util.c
@@ -26,6 +26,7 @@
#include <errno.h>
#include <stdbool.h>
#include <linux/errqueue.h>
+#include <getopt.h>
#include "util.h"
#include "iov.h"
@@ -694,3 +695,38 @@ const char *str_ee_origin(const struct sock_extended_err *ee)
return "<invalid>";
}
+
+/**
+ * close_open_files() - Close leaked files, but not --fd, stdin, stdout, stderr
+ * @argc: Argument count
+ * @argv: Command line options, as we need to skip any file given via --fd
+ */
+void close_open_files(int argc, char **argv)
+{
+ const struct option optfd[] = { { "fd", required_argument, NULL, 'F'
},
+ { 0 },
+ };
+ long fd = -1;
+ int name;
+
+ do {
+ name = getopt_long(argc, argv, ":F", optfd, NULL);
+
+ if (name == 'F') {
+ errno = 0;
+ fd = strtol(optarg, NULL, 0);
+
+ if (fd < 0 || errno)
+ die("Invalid --fd: %s", optarg);
+ }
+ } while (name != -1);
+
+ if (fd == -1) {
+ if (close_range(3, ~0U, CLOSE_RANGE_UNSHARE))
+ die_perror("Failed to close files leaked by parent");
+ } else {
+ if (close_range(3, fd - 1, CLOSE_RANGE_UNSHARE) ||
+ close_range(fd + 1, ~0U, CLOSE_RANGE_UNSHARE))
+ die_perror("Failed to close files leaked by parent");
+ }
+}
diff --git a/util.h b/util.h
index e8bf957..ab11ee7 100644
--- a/util.h
+++ b/util.h
@@ -183,6 +183,7 @@ int __daemon(int pidfile_fd, int devnull_fd);
int fls(unsigned long x);
int write_file(const char *path, const char *buf);
int write_remainder(int fd, const struct iovec *iov, size_t iovcnt, size_t skip);
+void close_open_files(int argc, char **argv);
/**
* af_name() - Return name of an address family
--
2.43.0