Merge tag 'vfs-6.14-rc2.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull vfs fixes from Christian Brauner:

 - Fix fsnotify FMODE_NONOTIFY* handling.

   This also disables fsnotify on all pseudo files by default apart from
   very select exceptions. This carries a regression risk so we need to
   watch out and adapt accordingly. However, it is overall a significant
   improvement over the current status quo where every rando file can
   get fsnotify enabled.

 - Cleanup and simplify lockref_init() after recent lockref changes.

 - Fix vboxfs build with gcc-15.

 - Add an assert into inode_set_cached_link() to catch corrupt links.

 - Allow users to also use an empty string check to detect whether a
   given mount option string was empty or not.

 - Fix how security options were appended to statmount()'s ->mnt_opt
   field.

 - Fix statmount() selftests to always check the returned mask.

 - Fix uninitialized value in vfs_statx_path().

 - Fix pidfs_ioctl() sanity checks to guard against ioctl() overloading
   and preserve extensibility.

* tag 'vfs-6.14-rc2.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  vfs: sanity check the length passed to inode_set_cached_link()
  pidfs: improve ioctl handling
  fsnotify: disable pre-content and permission events by default
  selftests: always check mask returned by statmount(2)
  fsnotify: disable notification by default for all pseudo files
  fs: fix adding security options to statmount.mnt_opt
  fsnotify: use accessor to set FMODE_NONOTIFY_*
  lockref: remove count argument of lockref_init
  gfs2: switch to lockref_init(..., 1)
  gfs2: use lockref_init for gl_lockref
  statmount: let unset strings be empty
  vboxsf: fix building with GCC 15
  fs/stat.c: avoid harmless garbage value problem in vfs_statx_path()

1 files changed, 11 insertions, 1 deletions

diff --git a/fs/pidfs.c b/fs/pidfs.c
index 049352f973de..63f9699ebac3 100644
--- a/fs/pidfs.c
+++ b/fs/pidfs.c
@@ -287,7 +287,6 @@ static bool pidfs_ioctl_valid(unsigned int cmd)
 	switch (cmd) {
 	case FS_IOC_GETVERSION:
 	case PIDFD_GET_CGROUP_NAMESPACE:
-	case PIDFD_GET_INFO:
 	case PIDFD_GET_IPC_NAMESPACE:
 	case PIDFD_GET_MNT_NAMESPACE:
 	case PIDFD_GET_NET_NAMESPACE:
@@ -300,6 +299,17 @@ static bool pidfs_ioctl_valid(unsigned int cmd)
 		return true;
 	}
 
+	/* Extensible ioctls require some more careful checks. */
+	switch (_IOC_NR(cmd)) {
+	case _IOC_NR(PIDFD_GET_INFO):
+		/*
+		 * Try to prevent performing a pidfd ioctl when someone
+		 * erronously mistook the file descriptor for a pidfd.
+		 * This is not perfect but will catch most cases.
+		 */
+		return (_IOC_TYPE(cmd) == _IOC_TYPE(PIDFD_GET_INFO));
+	}
+
 	return false;
 }