diff options
| -rw-r--r-- | fs/Makefile | 2 | ||||
| -rw-r--r-- | fs/pidfs.c | 122 | ||||
| -rw-r--r-- | kernel/fork.c | 110 |
3 files changed, 123 insertions, 111 deletions
diff --git a/fs/Makefile b/fs/Makefile index c09016257f05..125301673985 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -15,7 +15,7 @@ obj-y := open.o read_write.o file_table.o super.o \ pnode.o splice.o sync.o utimes.o d_path.o \ stack.o fs_struct.o statfs.o fs_pin.o nsfs.o \ fs_types.o fs_context.o fs_parser.o fsopen.o init.o \ - kernel_read_file.o mnt_idmapping.o remap_range.o + kernel_read_file.o mnt_idmapping.o remap_range.o pidfs.o obj-$(CONFIG_BUFFER_HEAD) += buffer.o mpage.o obj-$(CONFIG_PROC_FS) += proc_namespace.o diff --git a/fs/pidfs.c b/fs/pidfs.c new file mode 100644 index 000000000000..eccb291862a0 --- /dev/null +++ b/fs/pidfs.c @@ -0,0 +1,122 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/file.h> +#include <linux/fs.h> +#include <linux/magic.h> +#include <linux/mount.h> +#include <linux/pid.h> +#include <linux/pid_namespace.h> +#include <linux/poll.h> +#include <linux/proc_fs.h> +#include <linux/proc_ns.h> +#include <linux/pseudo_fs.h> +#include <linux/seq_file.h> +#include <uapi/linux/pidfd.h> + +static int pidfd_release(struct inode *inode, struct file *file) +{ + struct pid *pid = file->private_data; + + file->private_data = NULL; + put_pid(pid); + return 0; +} + +#ifdef CONFIG_PROC_FS +/** + * pidfd_show_fdinfo - print information about a pidfd + * @m: proc fdinfo file + * @f: file referencing a pidfd + * + * Pid: + * This function will print the pid that a given pidfd refers to in the + * pid namespace of the procfs instance. + * If the pid namespace of the process is not a descendant of the pid + * namespace of the procfs instance 0 will be shown as its pid. This is + * similar to calling getppid() on a process whose parent is outside of + * its pid namespace. + * + * NSpid: + * If pid namespaces are supported then this function will also print + * the pid of a given pidfd refers to for all descendant pid namespaces + * starting from the current pid namespace of the instance, i.e. the + * Pid field and the first entry in the NSpid field will be identical. + * If the pid namespace of the process is not a descendant of the pid + * namespace of the procfs instance 0 will be shown as its first NSpid + * entry and no others will be shown. + * Note that this differs from the Pid and NSpid fields in + * /proc/<pid>/status where Pid and NSpid are always shown relative to + * the pid namespace of the procfs instance. The difference becomes + * obvious when sending around a pidfd between pid namespaces from a + * different branch of the tree, i.e. where no ancestral relation is + * present between the pid namespaces: + * - create two new pid namespaces ns1 and ns2 in the initial pid + * namespace (also take care to create new mount namespaces in the + * new pid namespace and mount procfs) + * - create a process with a pidfd in ns1 + * - send pidfd from ns1 to ns2 + * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid + * have exactly one entry, which is 0 + */ +static void pidfd_show_fdinfo(struct seq_file *m, struct file *f) +{ + struct pid *pid = f->private_data; + struct pid_namespace *ns; + pid_t nr = -1; + + if (likely(pid_has_task(pid, PIDTYPE_PID))) { + ns = proc_pid_ns(file_inode(m->file)->i_sb); + nr = pid_nr_ns(pid, ns); + } + + seq_put_decimal_ll(m, "Pid:\t", nr); + +#ifdef CONFIG_PID_NS + seq_put_decimal_ll(m, "\nNSpid:\t", nr); + if (nr > 0) { + int i; + + /* If nr is non-zero it means that 'pid' is valid and that + * ns, i.e. the pid namespace associated with the procfs + * instance, is in the pid namespace hierarchy of pid. + * Start at one below the already printed level. + */ + for (i = ns->level + 1; i <= pid->level; i++) + seq_put_decimal_ll(m, "\t", pid->numbers[i].nr); + } +#endif + seq_putc(m, '\n'); +} +#endif + +/* + * Poll support for process exit notification. + */ +static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts) +{ + struct pid *pid = file->private_data; + bool thread = file->f_flags & PIDFD_THREAD; + struct task_struct *task; + __poll_t poll_flags = 0; + + poll_wait(file, &pid->wait_pidfd, pts); + /* + * Depending on PIDFD_THREAD, inform pollers when the thread + * or the whole thread-group exits. + */ + guard(rcu)(); + task = pid_task(pid, PIDTYPE_PID); + if (!task) + poll_flags = EPOLLIN | EPOLLRDNORM | EPOLLHUP; + else if (task->exit_state && (thread || thread_group_empty(task))) + poll_flags = EPOLLIN | EPOLLRDNORM; + + return poll_flags; +} + +const struct file_operations pidfd_fops = { + .release = pidfd_release, + .poll = pidfd_poll, +#ifdef CONFIG_PROC_FS + .show_fdinfo = pidfd_show_fdinfo, +#endif +}; diff --git a/kernel/fork.c b/kernel/fork.c index 3f22ec90c5c6..662a61f340ce 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1993,116 +1993,6 @@ struct pid *pidfd_pid(const struct file *file) return ERR_PTR(-EBADF); } -static int pidfd_release(struct inode *inode, struct file *file) -{ - struct pid *pid = file->private_data; - - file->private_data = NULL; - put_pid(pid); - return 0; -} - -#ifdef CONFIG_PROC_FS -/** - * pidfd_show_fdinfo - print information about a pidfd - * @m: proc fdinfo file - * @f: file referencing a pidfd - * - * Pid: - * This function will print the pid that a given pidfd refers to in the - * pid namespace of the procfs instance. - * If the pid namespace of the process is not a descendant of the pid - * namespace of the procfs instance 0 will be shown as its pid. This is - * similar to calling getppid() on a process whose parent is outside of - * its pid namespace. - * - * NSpid: - * If pid namespaces are supported then this function will also print - * the pid of a given pidfd refers to for all descendant pid namespaces - * starting from the current pid namespace of the instance, i.e. the - * Pid field and the first entry in the NSpid field will be identical. - * If the pid namespace of the process is not a descendant of the pid - * namespace of the procfs instance 0 will be shown as its first NSpid - * entry and no others will be shown. - * Note that this differs from the Pid and NSpid fields in - * /proc/<pid>/status where Pid and NSpid are always shown relative to - * the pid namespace of the procfs instance. The difference becomes - * obvious when sending around a pidfd between pid namespaces from a - * different branch of the tree, i.e. where no ancestral relation is - * present between the pid namespaces: - * - create two new pid namespaces ns1 and ns2 in the initial pid - * namespace (also take care to create new mount namespaces in the - * new pid namespace and mount procfs) - * - create a process with a pidfd in ns1 - * - send pidfd from ns1 to ns2 - * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid - * have exactly one entry, which is 0 - */ -static void pidfd_show_fdinfo(struct seq_file *m, struct file *f) -{ - struct pid *pid = f->private_data; - struct pid_namespace *ns; - pid_t nr = -1; - - if (likely(pid_has_task(pid, PIDTYPE_PID))) { - ns = proc_pid_ns(file_inode(m->file)->i_sb); - nr = pid_nr_ns(pid, ns); - } - - seq_put_decimal_ll(m, "Pid:\t", nr); - -#ifdef CONFIG_PID_NS - seq_put_decimal_ll(m, "\nNSpid:\t", nr); - if (nr > 0) { - int i; - - /* If nr is non-zero it means that 'pid' is valid and that - * ns, i.e. the pid namespace associated with the procfs - * instance, is in the pid namespace hierarchy of pid. - * Start at one below the already printed level. - */ - for (i = ns->level + 1; i <= pid->level; i++) - seq_put_decimal_ll(m, "\t", pid->numbers[i].nr); - } -#endif - seq_putc(m, '\n'); -} -#endif - -/* - * Poll support for process exit notification. - */ -static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts) -{ - struct pid *pid = file->private_data; - bool thread = file->f_flags & PIDFD_THREAD; - struct task_struct *task; - __poll_t poll_flags = 0; - - poll_wait(file, &pid->wait_pidfd, pts); - /* - * Depending on PIDFD_THREAD, inform pollers when the thread - * or the whole thread-group exits. - */ - rcu_read_lock(); - task = pid_task(pid, PIDTYPE_PID); - if (!task) - poll_flags = EPOLLIN | EPOLLRDNORM | EPOLLHUP; - else if (task->exit_state && (thread || thread_group_empty(task))) - poll_flags = EPOLLIN | EPOLLRDNORM; - rcu_read_unlock(); - - return poll_flags; -} - -const struct file_operations pidfd_fops = { - .release = pidfd_release, - .poll = pidfd_poll, -#ifdef CONFIG_PROC_FS - .show_fdinfo = pidfd_show_fdinfo, -#endif -}; - /** * __pidfd_prepare - allocate a new pidfd_file and reserve a pidfd * @pid: the struct pid for which to create a pidfd |