From: Oleg Nesterov <oleg@redhat.com>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Sargun Dhillon <sargun@sargun.me>,
linux-kernel@vger.kernel.org,
containers@lists.linux-foundation.org, linux-api@vger.kernel.org,
tycho@tycho.ws
Subject: Re: [RFC PATCH] ptrace: add PTRACE_GETFD request
Date: Fri, 6 Dec 2019 13:23:11 +0100 [thread overview]
Message-ID: <20191206122311.GA820@redhat.com> (raw)
In-Reply-To: <20191206082539.gmefytwu3ylixj5d@wittgenstein>
> On Thu, Dec 05, 2019 at 11:44:53PM +0000, Sargun Dhillon wrote:
>
> > +static int ptrace_getfd(struct task_struct *child, unsigned long fd)
> > +{
> > + struct files_struct *files;
> > + struct file *file;
> > + int ret = 0;
> > +
> > + files = get_files_struct(child);
> > + if (!files)
> > + return -ENOENT;
> > +
> > + spin_lock(&files->file_lock);
> > + file = fcheck_files(files, fd);
> > + if (!file)
> > + ret = -EBADF;
> > + else
> > + get_file(file);
> > + spin_unlock(&files->file_lock);
> > + put_files_struct(files);
may be someone can finally create a helper for this, it can have more users.
say,
struct file *get_task_file(task, fd)
{
struct file *file = NULL;
task_lock(task);
rcu_read_lock();
if (task->files) {
file = fcheck_files(task->files, fd);
if (file)
get_file(file);
}
rcu_read_unlock();
task_unlock(task);
return file;
}
no need to get/put files_struct, no need to take ->file_lock.
> > +
> > + if (ret)
> > + goto out;
> > +
> > + ret = get_unused_fd_flags(0);
> > + if (ret >= 0)
> > + fd_install(ret, file);
> > +
> > + fput(file);
this looks wrong or I am totally confused...
if (ret >= 0)
fd_install(file);
else
fput(file);
?
> > @@ -1265,7 +1299,8 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr,
> > }
> >
> > ret = ptrace_check_attach(child, request == PTRACE_KILL ||
> > - request == PTRACE_INTERRUPT);
> > + request == PTRACE_INTERRUPT ||
> > + request == PTRACE_GETFD);
Hmm. not sure why do you want this... But OK, we do not need to stop the tracee.
Oleg.
next prev parent reply other threads:[~2019-12-06 12:23 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-05 23:44 [RFC PATCH] ptrace: add PTRACE_GETFD request Sargun Dhillon
2019-12-06 2:38 ` Jann Horn
2019-12-06 6:16 ` Sargun Dhillon
2019-12-06 6:52 ` Aleksa Sarai
2019-12-06 8:25 ` Christian Brauner
2019-12-06 12:23 ` Oleg Nesterov [this message]
2019-12-06 14:10 ` Tycho Andersen
2019-12-06 19:03 ` Sargun Dhillon
2019-12-06 19:05 ` Jann Horn
2019-12-06 19:05 ` Jann Horn
2019-12-06 20:45 ` Andy Lutomirski
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