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| author | Christian Brauner <brauner@kernel.org> | 2026-04-16 13:58:57 +0300 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2026-05-21 16:33:48 +0300 |
| commit | 21688d812289d11ccf3018a94e0dfa2c98e73ec4 (patch) | |
| tree | 29fa743999d99a13dcfefd9e09bd90a14eecb44c /include/linux | |
| parent | 09e8b7a428b3f52b7625870edb4cd42e621fac07 (diff) | |
| parent | 6045a75399b45f6805f07a03020abf384b9f53c3 (diff) | |
| download | linux-21688d812289d11ccf3018a94e0dfa2c98e73ec4.tar.xz | |
Merge patch series "OPENAT2_REGULAR flag support for openat2"
Dorjoy Chowdhury <dorjoychy111@gmail.com> says:
I came upon this "Ability to only open regular files" uapi feature
suggestion from
https://uapi-group.org/kernel-features/#ability-to-only-open-regular-files
and thought it would be something I could do as a first patch and get to
know the kernel code a bit better.
The following filesystems have been tested by building and booting the
kernel x86 bzImage in a Fedora 43 VM in QEMU. I have tested with
OPENAT2_REGULAR that regular files can be successfully opened and
non-regular files (directory, fifo etc) return -EFTYPE.
- btrfs
- NFS (loopback)
- SMB (loopback)
Christian Brauner (Amutable) <brauner@kernel.org>:
All atomic_open implementations were audited for OPENAT2_REGULAR handling.
Explicit checks were added to ceph, gfs2, nfs (v4), and cifs/smb — these
are the filesystems whose atomic_open can encounter an existing non-regular
file and would otherwise call finish_open() on it or return a misleading
error code. The checks allow these filesystems to return -EFTYPE directly
and avoid unnecessary open+close round-trips.
The remaining implementations (9p, fuse, vboxsf, nfs v2/v3) don't need
explicit checks. They only call finish_open() on freshly created files
(always S_IFREG) and use finish_no_open() for lookup hits, letting the
VFS catch non-regular files via the do_open() safety net. Notably, fuse
also validates the server response (S_ISREG check on the reply) before
reaching finish_open().
* patches from https://patch.msgid.link/20260328172314.45807-1-dorjoychy111@gmail.com:
kselftest/openat2: test for OPENAT2_REGULAR flag
openat2: new OPENAT2_REGULAR flag support
Link: https://patch.msgid.link/20260328172314.45807-1-dorjoychy111@gmail.com
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/fcntl.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h index c65c5c73d362..6ad6b9e7a226 100644 --- a/include/linux/fcntl.h +++ b/include/linux/fcntl.h @@ -4,6 +4,7 @@ #include <linux/stat.h> #include <uapi/linux/fcntl.h> +#include <uapi/linux/openat2.h> /* List of all valid flags for the open/openat flags argument: */ #define VALID_OPEN_FLAGS \ @@ -12,6 +13,23 @@ FASYNC | O_DIRECT | O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW | \ O_NOATIME | O_CLOEXEC | O_PATH | __O_TMPFILE | O_EMPTYPATH) +/* List of all valid flags for openat2(2)'s how->flags argument. */ +#define VALID_OPENAT2_FLAGS (VALID_OPEN_FLAGS | OPENAT2_REGULAR) + +/* + * Kernel-internal carrier for OPENAT2_REGULAR. The UAPI bit lives in the + * upper 32 bits of open_how::flags so open()/openat() cannot encode it. + * build_open_flags() translates it to this internal flag, which then + * propagates through op->open_flag and f->f_flags exactly like __FMODE_EXEC. + * do_dentry_open() strips it so userspace cannot observe it via + * fcntl(F_GETFL). + * + * Bit 30 is not claimed by any O_* flag on any architecture and stays clear + * of the sign bit of the int op->open_flag. fcntl_init() enforces that it + * never aliases an open-flag bit. + */ +#define __O_REGULAR (1 << 30) + /* List of all valid flags for the how->resolve argument: */ #define VALID_RESOLVE_FLAGS \ (RESOLVE_NO_XDEV | RESOLVE_NO_MAGICLINKS | RESOLVE_NO_SYMLINKS | \ |