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Merge tag 'vfs-6.13.pidfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

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Pull pidfs update from Christian Brauner:
 "This adds a new ioctl to retrieve information about a pidfd.

  A common pattern when using pidfds is having to get information about
  the process, which currently requires /proc being mounted, resolving
  the fd to a pid, and then do manual string parsing of /proc/N/status
  and friends. This needs to be reimplemented over and over in all
  userspace projects (e.g.: it has been reimplemented in systemd, dbus,
  dbus-daemon, polkit so far), and requires additional care in checking
  that the fd is still valid after having parsed the data, to avoid
  races.

  Having a programmatic API that can be used directly removes all these
  requirements, including having /proc mounted.

  As discussed at LPC24, add an ioctl with an extensible struct so that
  more parameters can be added later if needed. Start with returning
  pid/tgid/ppid and some creds unconditionally, and cgroupid optionally"

* tag 'vfs-6.13.pidfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  pidfd: add ioctl to retrieve pid info
This commit is contained in:
Linus Torvalds
2024-11-18 10:47:46 -08:00
parent a29835c9d0 cdda1f26e7
commit 909d3b571e
3 changed files with 214 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

50
include/uapi/linux/pidfd.h
View File

@@ -16,6 +16,55 @@
#define PIDFD_SIGNAL_THREAD_GROUP (1UL << 1)
#define PIDFD_SIGNAL_PROCESS_GROUP (1UL << 2)
/* Flags for pidfd_info. */
#define PIDFD_INFO_PID (1UL << 0) /* Always returned, even if not requested */
#define PIDFD_INFO_CREDS (1UL << 1) /* Always returned, even if not requested */
#define PIDFD_INFO_CGROUPID (1UL << 2) /* Always returned if available, even if not requested */
#define PIDFD_INFO_SIZE_VER0 64 /* sizeof first published struct */
struct pidfd_info {
/*
* This mask is similar to the request_mask in statx(2).
*
* Userspace indicates what extensions or expensive-to-calculate fields
* they want by setting the corresponding bits in mask. The kernel
* will ignore bits that it does not know about.
*
* When filling the structure, the kernel will only set bits
* corresponding to the fields that were actually filled by the kernel.
* This also includes any future extensions that might be automatically
* filled. If the structure size is too small to contain a field
* (requested or not), to avoid confusion the mask will not
* contain a bit for that field.
*
* As such, userspace MUST verify that mask contains the
* corresponding flags after the ioctl(2) returns to ensure that it is
* using valid data.
*/
__u64 mask;
/*
* The information contained in the following fields might be stale at the
* time it is received, as the target process might have exited as soon as
* the IOCTL was processed, and there is no way to avoid that. However, it
* is guaranteed that if the call was successful, then the information was
* correct and referred to the intended process at the time the work was
* performed. */
__u64 cgroupid;
__u32 pid;
__u32 tgid;
__u32 ppid;
__u32 ruid;
__u32 rgid;
__u32 euid;
__u32 egid;
__u32 suid;
__u32 sgid;
__u32 fsuid;
__u32 fsgid;
__u32 spare0[1];
};
#define PIDFS_IOCTL_MAGIC 0xFF
#define PIDFD_GET_CGROUP_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 1)
@@ -28,5 +77,6 @@
#define PIDFD_GET_TIME_FOR_CHILDREN_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 8)
#define PIDFD_GET_USER_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 9)
#define PIDFD_GET_UTS_NAMESPACE _IO(PIDFS_IOCTL_MAGIC, 10)
#define PIDFD_GET_INFO _IOWR(PIDFS_IOCTL_MAGIC, 11, struct pidfd_info)
#endif /* _UAPI_LINUX_PIDFD_H */