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=== Description (from pull-request) ===
When no devpts devices are requested we used to return early but did not send a
response to the parent. This is a problem because the parent will be waiting
for a devpts fd to be sent. Make sure to always send a response.
Signed-off-by: Christian Brauner <christian.brau...@ubuntu.com>
From 68f3899e4aad1695fd31e5da47dcf3897d2ae2d9 Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brau...@ubuntu.com>
Date: Tue, 20 Oct 2020 13:02:00 +0200
Subject: [PATCH] conf: always send response to parent waiting for devptfs_fd
When no devpts devices are requested we used to return early but did not send a
response to the parent. This is a problem because the parent will be waiting
for a devpts fd to be sent. Make sure to always send a response.
Signed-off-by: Christian Brauner <christian.brau...@ubuntu.com>
---
src/lxc/conf.c | 34 ++++++++++++++++++++++++++--------
src/lxc/conf.h | 2 ++
src/lxc/start.c | 5 +----
3 files changed, 29 insertions(+), 12 deletions(-)
diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index b8058ffdce..e006ea4391 100644
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -1477,7 +1477,23 @@ static const struct id_map *find_mapped_nsid_entry(const
struct lxc_conf *conf,
return retmap;
}
-static int lxc_setup_devpts(struct lxc_handler *handler)
+int lxc_setup_devpts_parent(struct lxc_handler *handler)
+{
+ int ret;
+
+ if (handler->conf->pty_max <= 0)
+ return 0;
+
+ ret = lxc_abstract_unix_recv_fds(handler->data_sock[1],
&handler->conf->devpts_fd, 1,
+ &handler->conf->devpts_fd,
sizeof(handler->conf->devpts_fd));
+ if (ret < 0)
+ return log_error_errno(-1, errno, "Failed to receive devpts fd
from child");
+
+ TRACE("Received devpts file descriptor %d from child",
handler->conf->devpts_fd);
+ return 0;
+}
+
+static int lxc_setup_devpts_child(struct lxc_handler *handler)
{
__do_close int devpts_fd = -EBADF;
int ret;
@@ -1533,13 +1549,7 @@ static int lxc_setup_devpts(struct lxc_handler *handler)
if (devpts_fd < 0) {
devpts_fd = -EBADF;
TRACE("Failed to create detached devpts mount");
- ret = lxc_abstract_unix_send_fds(sock, NULL, 0, &devpts_fd,
sizeof(int));
- } else {
- ret = lxc_abstract_unix_send_fds(sock, &devpts_fd, 1, NULL, 0);
}
- if (ret < 0)
- return log_error_errno(-1, errno, "Failed to send devpts fd to
parent");
- TRACE("Sent devpts file descriptor %d to parent", devpts_fd);
/* Remove any pre-existing /dev/ptmx file. */
ret = remove("/dev/ptmx");
@@ -1575,6 +1585,14 @@ static int lxc_setup_devpts(struct lxc_handler *handler)
return log_error_errno(-1, errno, "Failed to create symlink
from \"/dev/ptmx\" to \"/dev/pts/ptmx\"");
DEBUG("Created symlink from \"/dev/ptmx\" to \"/dev/pts/ptmx\"");
+ if (devpts_fd < 0)
+ ret = lxc_abstract_unix_send_fds(sock, NULL, 0, &devpts_fd,
sizeof(int));
+ else
+ ret = lxc_abstract_unix_send_fds(sock, &devpts_fd, 1, NULL, 0);
+ if (ret < 0)
+ return log_error_errno(-1, errno, "Failed to send devpts fd to
parent");
+
+ TRACE("Sent devpts file descriptor %d to parent", devpts_fd);
return 0;
}
@@ -3392,7 +3410,7 @@ int lxc_setup(struct lxc_handler *handler)
if (lxc_conf->autodev > 0)
(void)lxc_setup_boot_id();
- ret = lxc_setup_devpts(handler);
+ ret = lxc_setup_devpts_child(handler);
if (ret < 0)
return log_error(-1, "Failed to setup new devpts instance");
diff --git a/src/lxc/conf.h b/src/lxc/conf.h
index cd54b3fe0f..ba06d42dc0 100644
--- a/src/lxc/conf.h
+++ b/src/lxc/conf.h
@@ -490,4 +490,6 @@ static inline int chown_mapped_root(const char *path, const
struct lxc_conf *con
return userns_exec_mapped_root(path, -EBADF, conf);
}
+__hidden int lxc_setup_devpts_parent(struct lxc_handler *handler);
+
#endif /* __LXC_CONF_H */
diff --git a/src/lxc/start.c b/src/lxc/start.c
index 7b29d40834..7bf7f8a2fb 100644
--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -1953,14 +1953,11 @@ static int lxc_spawn(struct lxc_handler *handler)
}
}
- ret = lxc_abstract_unix_recv_fds(data_sock1, &handler->conf->devpts_fd,
1,
- &handler->conf->devpts_fd,
- sizeof(handler->conf->devpts_fd));
+ ret = lxc_setup_devpts_parent(handler);
if (ret < 0) {
SYSERROR("Failed to receive devpts fd from child");
goto out_delete_net;
}
- TRACE("Received devpts file descriptor %d from child",
handler->conf->devpts_fd);
/* Now all networks are created, network devices are moved into place,
* and the correct names and ifindices in the respective namespaces have
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