>From 120b45b3900d28880b65b776f7a188cab4b38250 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Mon, 28 Oct 2024 15:34:59 +0100 Subject: [PATCH] UNTESTED, SKETCH, DRAFT Signed-off-by: Christian Brauner --- fs/pidfs.c | 42 +++++++++++++++++++++++++++++++++++++ include/linux/pidfs.h | 29 +++++++++++++++++++++++++ kernel/signal.c | 49 ++++++++++++------------------------------- 3 files changed, 84 insertions(+), 36 deletions(-) diff --git a/fs/pidfs.c b/fs/pidfs.c index 80675b6bf884..de7e9e6bbd22 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -22,6 +22,48 @@ #include "internal.h" #include "mount.h" +struct pid_fd pidfd_get(int fd) +{ + struct fd f; + struct pid *pid; + + /* handle PIDFD_SELF_* cases */ + if (fd < 0) { + if (fd == PIDFD_SELF_THREAD) + return (struct pid_fd){ .fd = EMPTY_FD, .pid = get_task_pid(current, PIDTYPE_PID) }; + if (fd == PIDFD_SELF_THREAD_GROUP) + return (struct pid_fd){ .fd = EMPTY_FD, .pid = get_task_pid(current, PIDTYPE_TGID) }; + return (struct pid_fd){ .fd = EMPTY_FD, .pid = ERR_PTR(-EBADF) }; + } + + /* handle the regular case */ + f = fdget(fd); + if (!fd_file(f)) + return (struct pid_fd){ .fd = EMPTY_FD, .pid = ERR_PTR(-EBADF) }; + + pid = pidfd_pid(fd_file(f)); + if (IS_ERR(pid)) { + fdput(f); + return (struct pid_fd) { .fd = EMPTY_FD, .pid = pid }; + } + + return (struct pid_fd) { .fd = f, pid = pid } ; +} + +void pidfd_put(struct pid_fd fd) +{ + /* + * Handle PIDFD_SELF_* where the struct pid hasn't been attached + * to a file. + */ + if (fd_empty(fd.fd) && pidfd_valid(fd)) + put_pid(fd.pid); + + /* Can call unconditionally safely. */ + fdput(fd.fd); + +} + #ifdef CONFIG_PROC_FS /** * pidfd_show_fdinfo - print information about a pidfd diff --git a/include/linux/pidfs.h b/include/linux/pidfs.h index 75bdf9807802..ad86b69ee1ea 100644 --- a/include/linux/pidfs.h +++ b/include/linux/pidfs.h @@ -2,6 +2,35 @@ #ifndef _LINUX_PID_FS_H #define _LINUX_PID_FS_H +#include +#include + +#define PIDFD_SELF PIDFD_SELF_THREAD +#define PIDFD_SELF_PROCESS PIDFD_SELF_THREAD_GROUP + +#define PIDFD_SELF_THREAD -10000 /* Current thread. */ +#define PIDFD_SELF_THREAD_GROUP -20000 /* Current thread group leader. */ + +struct pid_fd { + struct fd fd; + struct pid *pid; +}; + +static inline struct pid *pid_fd_pid(struct pid_fd pfd) +{ + return pfd.pid; +} + +static inline bool pidfd_valid(struct pid_fd pfd) +{ + return !IS_ERR(pid_fd_pid(pfd)); +} + +struct pid_fd pidfd_get(int fd); +void pidfd_put(struct pid_fd fd); + +DEFINE_CLASS(pid_fd, struct pid_fd, pidfd_put(_T), pidfd_get(fd), int fd) + struct file *pidfs_alloc_file(struct pid *pid, unsigned int flags); void __init pidfs_init(void); diff --git a/kernel/signal.c b/kernel/signal.c index 4344860ffcac..16b10e726038 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -47,6 +47,7 @@ #include #include #include +#include #include #define CREATE_TRACE_POINTS @@ -3875,17 +3876,6 @@ static int copy_siginfo_from_user_any(kernel_siginfo_t *kinfo, return copy_siginfo_from_user(kinfo, info); } -static struct pid *pidfd_to_pid(const struct file *file) -{ - struct pid *pid; - - pid = pidfd_pid(file); - if (!IS_ERR(pid)) - return pid; - - return tgid_pidfd_to_pid(file); -} - #define PIDFD_SEND_SIGNAL_FLAGS \ (PIDFD_SIGNAL_THREAD | PIDFD_SIGNAL_THREAD_GROUP | \ PIDFD_SIGNAL_PROCESS_GROUP) @@ -3908,7 +3898,6 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig, siginfo_t __user *, info, unsigned int, flags) { int ret; - struct fd f; struct pid *pid; kernel_siginfo_t kinfo; enum pid_type type; @@ -3921,25 +3910,18 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig, if (hweight32(flags & PIDFD_SEND_SIGNAL_FLAGS) > 1) return -EINVAL; - f = fdget(pidfd); - if (!fd_file(f)) - return -EBADF; - - /* Is this a pidfd? */ - pid = pidfd_to_pid(fd_file(f)); - if (IS_ERR(pid)) { - ret = PTR_ERR(pid); - goto err; - } + CLASS(pid_fd, pid_fd)(pidfd); + if (!pidfd_valid(pid_fd)) + return PTR_ERR(pid_fd_pid(pid_fd)); - ret = -EINVAL; + pid = pid_fd_pid(pid_fd); if (!access_pidfd_pidns(pid)) - goto err; + return -EINVAL; switch (flags) { case 0: /* Infer scope from the type of pidfd. */ - if (fd_file(f)->f_flags & PIDFD_THREAD) + if (pidfd > 0 && fd_file(pid_fd.fd)->f_flags & PIDFD_THREAD) type = PIDTYPE_PID; else type = PIDTYPE_TGID; @@ -3958,28 +3940,23 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig, if (info) { ret = copy_siginfo_from_user_any(&kinfo, info); if (unlikely(ret)) - goto err; + return ret; - ret = -EINVAL; if (unlikely(sig != kinfo.si_signo)) - goto err; + return -EINVAL; /* Only allow sending arbitrary signals to yourself. */ - ret = -EPERM; if ((task_pid(current) != pid || type > PIDTYPE_TGID) && (kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL)) - goto err; + return -EPERM; } else { prepare_kill_siginfo(sig, &kinfo, type); } if (type == PIDTYPE_PGID) - ret = kill_pgrp_info(sig, &kinfo, pid); - else - ret = kill_pid_info_type(sig, &kinfo, pid, type); -err: - fdput(f); - return ret; + return kill_pgrp_info(sig, &kinfo, pid); + + return kill_pid_info_type(sig, &kinfo, pid, type); } static int -- 2.45.2