path: root/kernel/exit.c
diff options
authorChristian Brauner <christian.brauner@ubuntu.com>2019-07-28 00:22:29 +0200
committerChristian Brauner <christian.brauner@ubuntu.com>2019-08-01 21:49:46 +0200
commit3695eae5fee0605f316fbaad0b9e3de791d7dfaf (patch)
treeaa5da8bb285ec7f45a9a19047ed7f6e10b37d55d /kernel/exit.c
parentLinus 5.3-rc1 (diff)
pidfd: add P_PIDFD to waitid()
This adds the P_PIDFD type to waitid(). One of the last remaining bits for the pidfd api is to make it possible to wait on pidfds. With P_PIDFD added to waitid() the parts of userspace that want to use the pidfd api to exclusively manage processes can do so now. One of the things this will unblock in the future is the ability to make it possible to retrieve the exit status via waitid(P_PIDFD) for non-parent processes if handed a _suitable_ pidfd that has this feature set. This is similar to what you can do on FreeBSD with kqueue(). It might even end up being possible to wait on a process as a non-parent if an appropriate property is enabled on the pidfd. With P_PIDFD no scoping of the process identified by the pidfd is possible, i.e. it explicitly blocks things such as wait4(-1), wait4(0), waitid(P_ALL), waitid(P_PGID) etc. It only allows for semantics equivalent to wait4(pid), waitid(P_PID). Users that need scoping should rely on pid-based wait*() syscalls for now. Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: David Howells <dhowells@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Andy Lutomirsky <luto@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Aleksa Sarai <cyphar@cyphar.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Link: https://lore.kernel.org/r/20190727222229.6516-2-christian@brauner.io
Diffstat (limited to 'kernel/exit.c')
1 files changed, 30 insertions, 3 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index a75b6a7f458a..64bb6893a37d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1552,6 +1552,23 @@ end:
return retval;
+static struct pid *pidfd_get_pid(unsigned int fd)
+ struct fd f;
+ struct pid *pid;
+ f = fdget(fd);
+ if (!f.file)
+ return ERR_PTR(-EBADF);
+ pid = pidfd_pid(f.file);
+ if (!IS_ERR(pid))
+ get_pid(pid);
+ fdput(f);
+ return pid;
static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
int options, struct rusage *ru)
@@ -1574,19 +1591,29 @@ static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
if (upid <= 0)
return -EINVAL;
+ pid = find_get_pid(upid);
case P_PGID:
if (upid <= 0)
return -EINVAL;
+ pid = find_get_pid(upid);
+ break;
+ case P_PIDFD:
+ type = PIDTYPE_PID;
+ if (upid < 0)
+ return -EINVAL;
+ pid = pidfd_get_pid(upid);
+ if (IS_ERR(pid))
+ return PTR_ERR(pid);
return -EINVAL;
- if (type < PIDTYPE_MAX)
- pid = find_get_pid(upid);
wo.wo_type = type;
wo.wo_pid = pid;
wo.wo_flags = options;