Use struct pid instead of user space pid values that are prone to wrap araound. In addition track the entire thread group instead of just the first thread that is started by exec. There are no multi-threaded user mode drivers today but there is nothing preclucing user drivers from being multi-threaded, so it is just a good idea to track the entire process. Take a reference count on the tgid's in question to make it possible to remove exit_umh in a future change. As a struct pid is available directly use kill_pid_info. The prior process signalling code was iffy in using a userspace pid known to be in the initial pid namespace and then looking up it's task in whatever the current pid namespace is. It worked only because kernel threads always run in the initial pid namespace. As the tgid is now refcounted verify the tgid is NULL at the start of fork_usermode_driver to avoid the possibility of silent pid leaks. v1: https://lkml.kernel.org/r/87mu4qdlv2.fsf_-_@xxxxxxxxxxxxxxxxxxxxx v2: https://lkml.kernel.org/r/a70l4oy8.fsf_-_@xxxxxxxxxxxxxxxxxxxxx Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> --- include/linux/usermode_driver.h | 2 +- kernel/exit.c | 3 ++- kernel/usermode_driver.c | 15 ++++++++++----- net/bpfilter/bpfilter_kern.c | 13 +++++-------- net/ipv4/bpfilter/sockopt.c | 3 ++- 5 files changed, 20 insertions(+), 16 deletions(-) diff --git a/include/linux/usermode_driver.h b/include/linux/usermode_driver.h index 97c919b7147c..45adbffb31d9 100644 --- a/include/linux/usermode_driver.h +++ b/include/linux/usermode_driver.h @@ -25,7 +25,7 @@ struct umd_info { struct list_head list; void (*cleanup)(struct umd_info *info); struct path wd; - pid_t pid; + struct pid *tgid; }; int umd_load_blob(struct umd_info *info, const void *data, size_t len); int umd_unload_blob(struct umd_info *info); diff --git a/kernel/exit.c b/kernel/exit.c index a081deea52ca..d3294b611df1 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -805,7 +805,8 @@ void __noreturn do_exit(long code) exit_task_namespaces(tsk); exit_task_work(tsk); exit_thread(tsk); - exit_umh(tsk); + if (group_dead) + exit_umh(tsk); /* * Flush inherited counters to the parent - before the parent diff --git a/kernel/usermode_driver.c b/kernel/usermode_driver.c index a86798759f83..f77f8d7ce9e3 100644 --- a/kernel/usermode_driver.c +++ b/kernel/usermode_driver.c @@ -133,7 +133,7 @@ static int umd_setup(struct subprocess_info *info, struct cred *new) set_fs_pwd(current->fs, &umd_info->wd); umd_info->pipe_to_umh = to_umh[1]; umd_info->pipe_from_umh = from_umh[0]; - umd_info->pid = task_pid_nr(current); + umd_info->tgid = get_pid(task_tgid(current)); current->flags |= PF_UMH; return 0; } @@ -146,6 +146,8 @@ static void umd_cleanup(struct subprocess_info *info) if (info->retval) { fput(umd_info->pipe_to_umh); fput(umd_info->pipe_from_umh); + put_pid(umd_info->tgid); + umd_info->tgid = NULL; } } @@ -155,9 +157,9 @@ static void umd_cleanup(struct subprocess_info *info) * * Returns either negative error or zero which indicates success in * executing a usermode driver. In such case 'struct umd_info *info' - * is populated with two pipes and a pid of the process. The caller is + * is populated with two pipes and a tgid of the process. The caller is * responsible for health check of the user process, killing it via - * pid, and closing the pipes when user process is no longer needed. + * tgid, and closing the pipes when user process is no longer needed. */ int fork_usermode_driver(struct umd_info *info) { @@ -165,6 +167,9 @@ int fork_usermode_driver(struct umd_info *info) char **argv = NULL; int err; + if (WARN_ON_ONCE(info->tgid)) + return -EBUSY; + err = -ENOMEM; argv = argv_split(GFP_KERNEL, info->driver_name, NULL); if (!argv) @@ -192,11 +197,11 @@ EXPORT_SYMBOL_GPL(fork_usermode_driver); void __exit_umh(struct task_struct *tsk) { struct umd_info *info; - pid_t pid = tsk->pid; + struct pid *tgid = task_tgid(tsk); mutex_lock(&umh_list_lock); list_for_each_entry(info, &umh_list, list) { - if (info->pid == pid) { + if (info->tgid == tgid) { list_del(&info->list); mutex_unlock(&umh_list_lock); goto out; diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c index 28883b00609d..08ea77c2b137 100644 --- a/net/bpfilter/bpfilter_kern.c +++ b/net/bpfilter/bpfilter_kern.c @@ -15,16 +15,13 @@ extern char bpfilter_umh_end; static void shutdown_umh(void) { - struct task_struct *tsk; + struct umd_info *info = &bpfilter_ops.info; + struct pid *tgid = info->tgid; if (bpfilter_ops.stop) return; - tsk = get_pid_task(find_vpid(bpfilter_ops.info.pid), PIDTYPE_PID); - if (tsk) { - send_sig(SIGKILL, tsk, 1); - put_task_struct(tsk); - } + kill_pid(tgid, SIGKILL, 1); } static void __stop_umh(void) @@ -48,7 +45,7 @@ static int __bpfilter_process_sockopt(struct sock *sk, int optname, req.cmd = optname; req.addr = (long __force __user)optval; req.len = optlen; - if (!bpfilter_ops.info.pid) + if (!bpfilter_ops.info.tgid) goto out; n = __kernel_write(bpfilter_ops.info.pipe_to_umh, &req, sizeof(req), &pos); @@ -81,7 +78,7 @@ static int start_umh(void) if (err) return err; bpfilter_ops.stop = false; - pr_info("Loaded bpfilter_umh pid %d\n", bpfilter_ops.info.pid); + pr_info("Loaded bpfilter_umh pid %d\n", pid_nr(bpfilter_ops.info.tgid)); /* health check that usermode process started correctly */ if (__bpfilter_process_sockopt(NULL, 0, NULL, 0, 0) != 0) { diff --git a/net/ipv4/bpfilter/sockopt.c b/net/ipv4/bpfilter/sockopt.c index 5050de28333d..56cbc43145f6 100644 --- a/net/ipv4/bpfilter/sockopt.c +++ b/net/ipv4/bpfilter/sockopt.c @@ -18,7 +18,8 @@ static void bpfilter_umh_cleanup(struct umd_info *info) bpfilter_ops.stop = true; fput(info->pipe_to_umh); fput(info->pipe_from_umh); - info->pid = 0; + put_pid(info->tgid); + info->tgid = NULL; mutex_unlock(&bpfilter_ops.lock); } -- 2.25.0
