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authorLinus Torvalds <torvalds@linux-foundation.org>2019-03-16 13:47:14 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-03-16 13:47:14 -0700
commita9dce6679d736cb3d612af39bab9f31f8db66f9b (patch)
tree7a5e010464d0154fce53aea3c9e3fac2b37c2912 /fs
parentf67e3fb4891287b8248ebb3320f794b9f5e782d4 (diff)
parent575a0ae9744d571f7c6aae4487a05850baae9e1c (diff)
Merge tag 'pidfd-v5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull pidfd system call from Christian Brauner: "This introduces the ability to use file descriptors from /proc/<pid>/ as stable handles on struct pid. Even if a pid is recycled the handle will not change. For a start these fds can be used to send signals to the processes they refer to. With the ability to use /proc/<pid> fds as stable handles on struct pid we can fix a long-standing issue where after a process has exited its pid can be reused by another process. If a caller sends a signal to a reused pid it will end up signaling the wrong process. With this patchset we enable a variety of use cases. One obvious example is that we can now safely delegate an important part of process management - sending signals - to processes other than the parent of a given process by sending file descriptors around via scm rights and not fearing that the given process will have been recycled in the meantime. It also allows for easy testing whether a given process is still alive or not by sending signal 0 to a pidfd which is quite handy. There has been some interest in this feature e.g. from systems management (systemd, glibc) and container managers. I have requested and gotten comments from glibc to make sure that this syscall is suitable for their needs as well. In the future I expect it to take on most other pid-based signal syscalls. But such features are left for the future once they are needed. This has been sitting in linux-next for quite a while and has not caused any issues. It comes with selftests which verify basic functionality and also test that a recycled pid cannot be signaled via a pidfd. Jon has written about a prior version of this patchset. It should cover the basic functionality since not a lot has changed since then: https://lwn.net/Articles/773459/ The commit message for the syscall itself is extensively documenting the syscall, including it's functionality and extensibility" * tag 'pidfd-v5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: selftests: add tests for pidfd_send_signal() signal: add pidfd_send_signal() syscall
Diffstat (limited to 'fs')
-rw-r--r--fs/proc/base.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index f5ebdd87afb2..ddef482f1334 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3074,6 +3074,15 @@ static const struct file_operations proc_tgid_base_operations = {
.llseek = generic_file_llseek,
};
+struct pid *tgid_pidfd_to_pid(const struct file *file)
+{
+ if (!d_is_dir(file->f_path.dentry) ||
+ (file->f_op != &proc_tgid_base_operations))
+ return ERR_PTR(-EBADF);
+
+ return proc_pid(file_inode(file));
+}
+
static struct dentry *proc_tgid_base_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
return proc_pident_lookup(dir, dentry,