* Anonymous inodes currently don't come with a proper mode causing
issues in the kernel when we want to add useful VFS debug assert. Fix
that by giving them a proper mode and masking it off when we report it
to userspace which relies on them not having any mode.
* Anonymous inodes currently allow to change inode attributes because
the VFS falls back to simple_setattr() if i_op->setattr isn't
implemented. This means the ownership and mode for every single user
of anon_inode_inode can be changed. Block that as it's either useless
or actively harmful. If specific ownership is needed the respective
subsystem should allocate anonymous inodes from their own private
superblock.
* Port pidfs to the new anon_inode_{g,s}etattr() helpers.
* Add proper tests for anonymous inode behavior.
The anonymous inode specific fixes should ideally be backported to all
LTS kernels.
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
---
Christian Brauner (9):
anon_inode: use a proper mode internally
pidfs: use anon_inode_getattr()
anon_inode: explicitly block ->setattr()
pidfs: use anon_inode_setattr()
anon_inode: raise SB_I_NODEV and SB_I_NOEXEC
selftests/filesystems: add first test for anonymous inodes
selftests/filesystems: add second test for anonymous inodes
selftests/filesystems: add third test for anonymous inodes
selftests/filesystems: add fourth test for anonymous inodes
fs/anon_inodes.c | 45 ++++++++++++++
fs/internal.h | 5 ++
fs/libfs.c | 2 +-
fs/pidfs.c | 26 +-------
tools/testing/selftests/filesystems/.gitignore | 1 +
tools/testing/selftests/filesystems/Makefile | 2 +-
.../selftests/filesystems/anon_inode_test.c | 69 ++++++++++++++++++++++
7 files changed, 124 insertions(+), 26 deletions(-)
---
base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
change-id: 20250407-work-anon_inode-e22bb1a74992
