[PATCH v6 6/6] fs: introduce file_getattr and file_setattr syscalls

Andrey Albershteyn
2025-06-30T16:20:41Z

From: Andrey Albershteyn <aalbersh@redhat.com>

Introduce file_getattr() and file_setattr() syscalls to manipulate inode
extended attributes. The syscalls takes pair of file descriptor and
pathname. Then it operates on inode opened accroding to openat()
semantics. The struct fsx_fileattr is passed to obtain/change extended
attributes.

This is an alternative to FS_IOC_FSSETXATTR ioctl with a difference
that file don't need to be open as we can reference it with a path
instead of fd. By having this we can manipulated inode extended
attributes not only on regular files but also on special ones. This
is not possible with FS_IOC_FSSETXATTR ioctl as with special files
we can not call ioctl() directly on the filesystem inode using fd.

This patch adds two new syscalls which allows userspace to get/set
extended inode attributes on special files by using parent directory
and a path - *at() like syscall.

CC: linux-api@vger.kernel.org
CC: linux-fsdevel@vger.kernel.org
CC: linux-xfs@vger.kernel.org
Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
---
arch/alpha/kernel/syscalls/syscall.tbl | 2 +
arch/arm/tools/syscall.tbl | 2 +
arch/arm64/tools/syscall_32.tbl | 2 +
arch/m68k/kernel/syscalls/syscall.tbl | 2 +
arch/microblaze/kernel/syscalls/syscall.tbl | 2 +
arch/mips/kernel/syscalls/syscall_n32.tbl | 2 +
arch/mips/kernel/syscalls/syscall_n64.tbl | 2 +
arch/mips/kernel/syscalls/syscall_o32.tbl | 2 +
arch/parisc/kernel/syscalls/syscall.tbl | 2 +
arch/powerpc/kernel/syscalls/syscall.tbl | 2 +
arch/s390/kernel/syscalls/syscall.tbl | 2 +
arch/sh/kernel/syscalls/syscall.tbl | 2 +
arch/sparc/kernel/syscalls/syscall.tbl | 2 +
arch/x86/entry/syscalls/syscall_32.tbl | 2 +
arch/x86/entry/syscalls/syscall_64.tbl | 2 +
arch/xtensa/kernel/syscalls/syscall.tbl | 2 +
fs/file_attr.c | 148 ++++++++++++++++++++++++++++
include/linux/syscalls.h | 6 ++
include/uapi/asm-generic/unistd.h | 8 +-
include/uapi/linux/fs.h | 18 ++++
scripts/syscall.tbl | 2 +
21 files changed, 213 insertions(+), 1 deletion(-)

diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl
index 2dd6340de6b4..16dca28ebf17 100644
--- a/arch/alpha/kernel/syscalls/syscall.tbl
+++ b/arch/alpha/kernel/syscalls/syscall.tbl
@@ -507,3 +507,5 @@
575 common listxattrat sys_listxattrat
576 common removexattrat sys_removexattrat
577 common open_tree_attr sys_open_tree_attr
+578 common file_getattr sys_file_getattr
+579 common file_setattr sys_file_setattr
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index 27c1d5ebcd91..b07e699aaa3c 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -482,3 +482,5 @@
465 common listxattrat sys_listxattrat
466 common removexattrat sys_removexattrat
467 common open_tree_attr sys_open_tree_attr
+468 common file_getattr sys_file_getattr
+469 common file_setattr sys_file_setattr
diff --git a/arch/arm64/tools/syscall_32.tbl b/arch/arm64/tools/syscall_32.tbl
index 0765b3a8d6d6..8d9088bc577d 100644
--- a/arch/arm64/tools/syscall_32.tbl
+++ b/arch/arm64/tools/syscall_32.tbl
@@ -479,3 +479,5 @@
465 common listxattrat sys_listxattrat
466 common removexattrat sys_removexattrat
467 common open_tree_attr sys_open_tree_attr
+468 common file_getattr sys_file_getattr
+469 common file_setattr sys_file_setattr
diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl
index 9fe47112c586..f41d38dfbf13 100644
--- a/arch/m68k/kernel/syscalls/syscall.tbl
+++ b/arch/m68k/kernel/syscalls/syscall.tbl
@@ -467,3 +467,5 @@
465 common listxattrat sys_listxattrat
466 common removexattrat sys_removexattrat
467 common open_tree_attr sys_open_tree_attr
+468 common file_getattr sys_file_getattr
+469 common file_setattr sys_file_setattr
diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index 7b6e97828e55..580af574fe73 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -473,3 +473,5 @@
465 common listxattrat sys_listxattrat
466 common removexattrat sys_removexattrat
467 common open_tree_attr sys_open_tree_attr
+468 common file_getattr sys_file_getattr
+469 common file_setattr sys_file_setattr
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index aa70e371bb54..d824ffe9a014 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -406,3 +406,5 @@
465 n32 listxattrat sys_listxattrat
466 n32 removexattrat sys_removexattrat
467 n32 open_tree_attr sys_open_tree_attr
+468 n32 file_getattr sys_file_getattr
+469 n32 file_setattr sys_file_setattr
diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
index 1e8c44c7b614..7a7049c2c307 100644
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -382,3 +382,5 @@
465 n64 listxattrat sys_listxattrat
466 n64 removexattrat sys_removexattrat
467 n64 open_tree_attr sys_open_tree_attr
+468 n64 file_getattr sys_file_getattr
+469 n64 file_setattr sys_file_setattr
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index 114a5a1a6230..d330274f0601 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -455,3 +455,5 @@
465 o32 listxattrat sys_listxattrat
466 o32 removexattrat sys_removexattrat
467 o32 open_tree_attr sys_open_tree_attr
+468 o32 file_getattr sys_file_getattr
+469 o32 file_setattr sys_file_setattr
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index 94df3cb957e9..88a788a7b18d 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -466,3 +466,5 @@
465 common listxattrat sys_listxattrat
466 common removexattrat sys_removexattrat
467 common open_tree_attr sys_open_tree_attr
+468 common file_getattr sys_file_getattr
+469 common file_setattr sys_file_setattr
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 9a084bdb8926..b453e80dfc00 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -558,3 +558,5 @@
465 common listxattrat sys_listxattrat
466 common removexattrat sys_removexattrat
467 common open_tree_attr sys_open_tree_attr
+468 common file_getattr sys_file_getattr
+469 common file_setattr sys_file_setattr
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index a4569b96ef06..8a6744d658db 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -470,3 +470,5 @@
465 common listxattrat sys_listxattrat sys_listxattrat
466 common removexattrat sys_removexattrat sys_removexattrat
467 common open_tree_attr sys_open_tree_attr sys_open_tree_attr
+468 common file_getattr sys_file_getattr sys_file_getattr
+469 common file_setattr sys_file_setattr sys_file_setattr
diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl
index 52a7652fcff6..5e9c9eff5539 100644
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -471,3 +471,5 @@
465 common listxattrat sys_listxattrat
466 common removexattrat sys_removexattrat
467 common open_tree_attr sys_open_tree_attr
+468 common file_getattr sys_file_getattr
+469 common file_setattr sys_file_setattr
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index 83e45eb6c095..ebb7d06d1044 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -513,3 +513,5 @@
465 common listxattrat sys_listxattrat
466 common removexattrat sys_removexattrat
467 common open_tree_attr sys_open_tree_attr
+468 common file_getattr sys_file_getattr
+469 common file_setattr sys_file_setattr
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index ac007ea00979..4877e16da69a 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -473,3 +473,5 @@
465 i386 listxattrat sys_listxattrat
466 i386 removexattrat sys_removexattrat
467 i386 open_tree_attr sys_open_tree_attr
+468 i386 file_getattr sys_file_getattr
+469 i386 file_setattr sys_file_setattr
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index cfb5ca41e30d..92cf0fe2291e 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -391,6 +391,8 @@
465 common listxattrat sys_listxattrat
466 common removexattrat sys_removexattrat
467 common open_tree_attr sys_open_tree_attr
+468 common file_getattr sys_file_getattr
+469 common file_setattr sys_file_setattr

#
# Due to a historical design error, certain syscalls are numbered differently
diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl
index f657a77314f8..374e4cb788d8 100644
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -438,3 +438,5 @@
465 common listxattrat sys_listxattrat
466 common removexattrat sys_removexattrat
467 common open_tree_attr sys_open_tree_attr
+468 common file_getattr sys_file_getattr
+469 common file_setattr sys_file_setattr
diff --git a/fs/file_attr.c b/fs/file_attr.c
index 62f08872d4ad..fda9d847eee5 100644
--- a/fs/file_attr.c
+++ b/fs/file_attr.c
@@ -3,6 +3,10 @@
#include <linux/security.h>
#include <linux/fscrypt.h>
#include <linux/fileattr.h>
+#include <linux/syscalls.h>
+#include <linux/namei.h>
+
+#include "internal.h"

/**
* fileattr_fill_xflags - initialize fileattr with xflags
@@ -89,6 +93,19 @@ int vfs_fileattr_get(struct dentry *dentry, struct fileattr *fa)
}
EXPORT_SYMBOL(vfs_fileattr_get);

+static void fileattr_to_fsx_fileattr(const struct fileattr *fa,
+ struct fsx_fileattr *fsx)
+{
+ __u32 mask = FS_XFLAGS_MASK;
+
+ memset(fsx, 0, sizeof(struct fsx_fileattr));
+ fsx->fsx_xflags = fa->fsx_xflags & mask;
+ fsx->fsx_extsize = fa->fsx_extsize;
+ fsx->fsx_nextents = fa->fsx_nextents;
+ fsx->fsx_projid = fa->fsx_projid;
+ fsx->fsx_cowextsize = fa->fsx_cowextsize;
+}
+
/**
* copy_fsxattr_to_user - copy fsxattr to userspace.
* @fa: fileattr pointer
@@ -115,6 +132,23 @@ int copy_fsxattr_to_user(const struct fileattr *fa, struct fsxattr __user *ufa)
}
EXPORT_SYMBOL(copy_fsxattr_to_user);

+static int fsx_fileattr_to_fileattr(const struct fsx_fileattr *fsx,
+ struct fileattr *fa)
+{
+ __u32 mask = FS_XFLAGS_MASK;
+
+ if (fsx->fsx_xflags & ~mask)
+ return -EINVAL;
+
+ fileattr_fill_xflags(fa, fsx->fsx_xflags);
+ fa->fsx_xflags &= ~FS_XFLAG_RDONLY_MASK;
+ fa->fsx_extsize = fsx->fsx_extsize;
+ fa->fsx_projid = fsx->fsx_projid;
+ fa->fsx_cowextsize = fsx->fsx_cowextsize;
+
+ return 0;
+}
+
static int copy_fsxattr_from_user(struct fileattr *fa,
struct fsxattr __user *ufa)
{
@@ -343,3 +377,117 @@ int ioctl_fssetxattr(struct file *file, void __user *argp)
return err;
}
EXPORT_SYMBOL(ioctl_fssetxattr);
+
+SYSCALL_DEFINE5(file_getattr, int, dfd, const char __user *, filename,
+ struct fsx_fileattr __user *, ufsx, size_t, usize,
+ unsigned int, at_flags)
+{
+ struct fileattr fa;
+ struct path filepath __free(path_put) = {};
+ int error;
+ unsigned int lookup_flags = 0;
+ struct filename *name __free(putname) = NULL;
+ struct fsx_fileattr fsx;
+
+ BUILD_BUG_ON(sizeof(struct fsx_fileattr) < FSX_FILEATTR_SIZE_VER0);
+ BUILD_BUG_ON(sizeof(struct fsx_fileattr) != FSX_FILEATTR_SIZE_LATEST);
+
+ if ((at_flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
+ return -EINVAL;
+
+ if (!(at_flags & AT_SYMLINK_NOFOLLOW))
+ lookup_flags |= LOOKUP_FOLLOW;
+
+ if (usize > PAGE_SIZE)
+ return -E2BIG;
+
+ if (usize < FSX_FILEATTR_SIZE_VER0)
+ return -EINVAL;
+
+ name = getname_maybe_null(filename, at_flags);
+ if (IS_ERR(name))
+ return PTR_ERR(name);
+
+ if (!name && dfd >= 0) {
+ CLASS(fd, f)(dfd);
+
+ filepath = fd_file(f)->f_path;
+ path_get(&filepath);
+ } else {
+ error = filename_lookup(dfd, name, lookup_flags, &filepath,
+ NULL);
+ if (error)
+ return error;
+ }
+
+ error = vfs_fileattr_get(filepath.dentry, &fa);
+ if (error)
+ return error;
+
+ fileattr_to_fsx_fileattr(&fa, &fsx);
+ error = copy_struct_to_user(ufsx, usize, &fsx,
+ sizeof(struct fsx_fileattr), NULL);
+
+ return error;
+}
+
+SYSCALL_DEFINE5(file_setattr, int, dfd, const char __user *, filename,
+ struct fsx_fileattr __user *, ufsx, size_t, usize,
+ unsigned int, at_flags)
+{
+ struct fileattr fa;
+ struct path filepath __free(path_put) = {};
+ int error;
+ unsigned int lookup_flags = 0;
+ struct filename *name __free(putname) = NULL;
+ struct fsx_fileattr fsx;
+
+ BUILD_BUG_ON(sizeof(struct fsx_fileattr) < FSX_FILEATTR_SIZE_VER0);
+ BUILD_BUG_ON(sizeof(struct fsx_fileattr) != FSX_FILEATTR_SIZE_LATEST);
+
+ if ((at_flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
+ return -EINVAL;
+
+ if (!(at_flags & AT_SYMLINK_NOFOLLOW))
+ lookup_flags |= LOOKUP_FOLLOW;
+
+ if (usize > PAGE_SIZE)
+ return -E2BIG;
+
+ if (usize < FSX_FILEATTR_SIZE_VER0)
+ return -EINVAL;
+
+ error = copy_struct_from_user(&fsx, sizeof(struct fsx_fileattr), ufsx,
+ usize);
+ if (error)
+ return error;
+
+ error = fsx_fileattr_to_fileattr(&fsx, &fa);
+ if (error)
+ return error;
+
+ name = getname_maybe_null(filename, at_flags);
+ if (IS_ERR(name))
+ return PTR_ERR(name);
+
+ if (!name && dfd >= 0) {
+ CLASS(fd, f)(dfd);
+
+ filepath = fd_file(f)->f_path;
+ path_get(&filepath);
+ } else {
+ error = filename_lookup(dfd, name, lookup_flags, &filepath,
+ NULL);
+ if (error)
+ return error;
+ }
+
+ error = mnt_want_write(filepath.mnt);
+ if (!error) {
+ error = vfs_fileattr_set(mnt_idmap(filepath.mnt),
+ filepath.dentry, &fa);
+ mnt_drop_write(filepath.mnt);
+ }
+
+ return error;
+}
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index e5603cc91963..179acbe28fec 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -371,6 +371,12 @@ asmlinkage long sys_removexattrat(int dfd, const char __user *path,
asmlinkage long sys_lremovexattr(const char __user *path,
const char __user *name);
asmlinkage long sys_fremovexattr(int fd, const char __user *name);
+asmlinkage long sys_file_getattr(int dfd, const char __user *filename,
+ struct fsx_fileattr __user *ufsx, size_t usize,
+ unsigned int at_flags);
+asmlinkage long sys_file_setattr(int dfd, const char __user *filename,
+ struct fsx_fileattr __user *ufsx, size_t usize,
+ unsigned int at_flags);
asmlinkage long sys_getcwd(char __user *buf, unsigned long size);
asmlinkage long sys_eventfd2(unsigned int count, int flags);
asmlinkage long sys_epoll_create1(int flags);
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index 2892a45023af..04e0077fb4c9 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -852,8 +852,14 @@ __SYSCALL(__NR_removexattrat, sys_removexattrat)
#define __NR_open_tree_attr 467
__SYSCALL(__NR_open_tree_attr, sys_open_tree_attr)

+/* fs/inode.c */
+#define __NR_file_getattr 468
+__SYSCALL(__NR_file_getattr, sys_file_getattr)
+#define __NR_file_setattr 469
+__SYSCALL(__NR_file_setattr, sys_file_setattr)
+
#undef __NR_syscalls
-#define __NR_syscalls 468
+#define __NR_syscalls 470

/*
* 32 bit systems traditionally used different
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 0098b0ce8ccb..0784f2033ba4 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -148,6 +148,24 @@ struct fsxattr {
unsigned char fsx_pad[8];
};

+/*
+ * Variable size structure for file_[sg]et_attr().
+ *
+ * Note. This is alternative to the structure 'struct fileattr'/'struct fsxattr'.
+ * As this structure is passed to/from userspace with its size, this can
+ * be versioned based on the size.
+ */
+struct fsx_fileattr {
+ __u32 fsx_xflags; /* xflags field value (get/set) */
+ __u32 fsx_extsize; /* extsize field value (get/set)*/
+ __u32 fsx_nextents; /* nextents field value (get) */
+ __u32 fsx_projid; /* project identifier (get/set) */
+ __u32 fsx_cowextsize; /* CoW extsize field value (get/set) */
+};
+
+#define FSX_FILEATTR_SIZE_VER0 20
+#define FSX_FILEATTR_SIZE_LATEST FSX_FILEATTR_SIZE_VER0
+
/*
* Flags for the fsx_xflags field
*/
diff --git a/scripts/syscall.tbl b/scripts/syscall.tbl
index 580b4e246aec..d1ae5e92c615 100644
--- a/scripts/syscall.tbl
+++ b/scripts/syscall.tbl
@@ -408,3 +408,5 @@
465 common listxattrat sys_listxattrat
466 common removexattrat sys_removexattrat
467 common open_tree_attr sys_open_tree_attr
+468 common file_getattr sys_file_getattr
+469 common file_setattr sys_file_setattr

--
2.47.2