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authorStefano Brivio <sbrivio@redhat.com>2023-05-21 14:50:11 +0200
committerStefano Brivio <sbrivio@redhat.com>2023-05-23 16:13:28 +0200
commitb0e450aa8500648cc89ca4f68b6a6155267ccd9d (patch)
treede7d5fb94cdcfab8a6005c31c165d4d4a756b114
parentb0881aae6d91845821b2732f3fc8890e3d9ec4d2 (diff)
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pasta: Detach mount namespace, (re)mount procfs before spawning command
If we want /proc contents to be consistent after pasta spawns a child process in a new PID namespace (only for operation without a pre-existing namespace), we need to mount /proc after the clone(2) call with CLONE_NEWPID, and we enable the child to do that by passing, in the same call, the CLONE_NEWNS flag, as described by pid_namespaces(7). This is not really a remount: in fact, passing MS_REMOUNT to mount(2) would make the call fail. We're in another mount namespace now, so it's a fresh mount that has the effect of hiding the existing one. Signed-off-by: Stefano Brivio <sbrivio@redhat.com> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
-rw-r--r--pasta.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/pasta.c b/pasta.c
index 3a4d704..b30ce70 100644
--- a/pasta.c
+++ b/pasta.c
@@ -29,6 +29,7 @@
#include <syslog.h>
#include <sys/epoll.h>
#include <sys/inotify.h>
+#include <sys/mount.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
@@ -172,6 +173,10 @@ static int pasta_spawn_cmd(void *arg)
const struct pasta_spawn_cmd_arg *a;
sigset_t set;
+ /* We run in a detached PID and mount namespace: mount /proc over */
+ if (mount("", "/proc", "proc", 0, NULL))
+ warn("Couldn't mount /proc: %s", strerror(errno));
+
if (write_file("/proc/sys/net/ipv4/ping_group_range", "0 0"))
warn("Cannot set ping_group_range, ICMP requests might fail");
@@ -243,7 +248,7 @@ void pasta_start_ns(struct ctx *c, uid_t uid, gid_t gid,
pasta_child_pid = do_clone(pasta_spawn_cmd, ns_fn_stack,
sizeof(ns_fn_stack),
CLONE_NEWIPC | CLONE_NEWPID | CLONE_NEWNET |
- CLONE_NEWUTS | SIGCHLD,
+ CLONE_NEWUTS | CLONE_NEWNS | SIGCHLD,
(void *)&arg);
if (pasta_child_pid == -1) {