fs: introduce file_getattr and file_setattr syscalls

alberand · brauner · commit be7efb2d20d6 · 2025-07-02T17:05:17.000+02:00
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 file_attr 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> Link: https://lore.kernel.org/20250630-xattrat-syscall-v6-6-c4e3bc35227b@kernel.org Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Christian Brauner <brauner@kernel.org>
diff --git 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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -4,6 +4,10 @@
 #include <linux/fscrypt.h>
 #include <linux/fileattr.h>
 #include <linux/export.h>
+#include <linux/syscalls.h>
+#include <linux/namei.h>
+
+#include "internal.h"
 
 /**
  * fileattr_fill_xflags - initialize fileattr with xflags
@@ -90,6 +94,19 @@ int vfs_fileattr_get(struct dentry *dentry, struct fileattr *fa)
 }
 EXPORT_SYMBOL(vfs_fileattr_get);
 
+static void fileattr_to_file_attr(const struct fileattr *fa,
+				  struct file_attr *fattr)
+{
+	__u32 mask = FS_XFLAGS_MASK;
+
+	memset(fattr, 0, sizeof(struct file_attr));
+	fattr->fa_xflags = fa->fsx_xflags & mask;
+	fattr->fa_extsize = fa->fsx_extsize;
+	fattr->fa_nextents = fa->fsx_nextents;
+	fattr->fa_projid = fa->fsx_projid;
+	fattr->fa_cowextsize = fa->fsx_cowextsize;
+}
+
 /**
  * copy_fsxattr_to_user - copy fsxattr to userspace.
  * @fa:		fileattr pointer
@@ -116,6 +133,23 @@ int copy_fsxattr_to_user(const struct fileattr *fa, struct fsxattr __user *ufa)
 }
 EXPORT_SYMBOL(copy_fsxattr_to_user);
 
+static int file_attr_to_fileattr(const struct file_attr *fattr,
+				 struct fileattr *fa)
+{
+	__u32 mask = FS_XFLAGS_MASK;
+
+	if (fattr->fa_xflags & ~mask)
+		return -EINVAL;
+
+	fileattr_fill_xflags(fa, fattr->fa_xflags);
+	fa->fsx_xflags &= ~FS_XFLAG_RDONLY_MASK;
+	fa->fsx_extsize = fattr->fa_extsize;
+	fa->fsx_projid = fattr->fa_projid;
+	fa->fsx_cowextsize = fattr->fa_cowextsize;
+
+	return 0;
+}
+
 static int copy_fsxattr_from_user(struct fileattr *fa,
 				  struct fsxattr __user *ufa)
 {
@@ -344,3 +378,121 @@ 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 file_attr __user *, ufattr, size_t, usize,
+		unsigned int, at_flags)
+{
+	struct path filepath __free(path_put) = {};
+	struct filename *name __free(putname) = NULL;
+	unsigned int lookup_flags = 0;
+	struct file_attr fattr;
+	struct fileattr fa;
+	int error;
+
+	BUILD_BUG_ON(sizeof(struct file_attr) < FILE_ATTR_SIZE_VER0);
+	BUILD_BUG_ON(sizeof(struct file_attr) != FILE_ATTR_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 < FILE_ATTR_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);
+		if (fd_empty(f))
+			return -EBADF;
+
+		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_file_attr(&fa, &fattr);
+	error = copy_struct_to_user(ufattr, usize, &fattr,
+				    sizeof(struct file_attr), NULL);
+
+	return error;
+}
+
+SYSCALL_DEFINE5(file_setattr, int, dfd, const char __user *, filename,
+		struct file_attr __user *, ufattr, size_t, usize,
+		unsigned int, at_flags)
+{
+	struct path filepath __free(path_put) = {};
+	struct filename *name __free(putname) = NULL;
+	unsigned int lookup_flags = 0;
+	struct file_attr fattr;
+	struct fileattr fa;
+	int error;
+
+	BUILD_BUG_ON(sizeof(struct file_attr) < FILE_ATTR_SIZE_VER0);
+	BUILD_BUG_ON(sizeof(struct file_attr) != FILE_ATTR_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 < FILE_ATTR_SIZE_VER0)
+		return -EINVAL;
+
+	error = copy_struct_from_user(&fattr, sizeof(struct file_attr), ufattr,
+				      usize);
+	if (error)
+		return error;
+
+	error = file_attr_to_fileattr(&fattr, &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);
+		if (fd_empty(f))
+			return -EBADF;
+
+		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
@@ -78,6 +78,7 @@ struct cachestat;
 struct statmount;
 struct mnt_id_req;
 struct xattr_args;
+struct file_attr;
 
 #include <linux/types.h>
 #include <linux/aio_abi.h>
@@ -371,6 +372,12 @@ 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 file_attr __user *attr, size_t usize,
+				 unsigned int at_flags);
+asmlinkage long sys_file_setattr(int dfd, const char __user *filename,
+				 struct file_attr __user *attr, 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
@@ -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
@@ -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 file_attr {
+	__u64 fa_xflags;	/* xflags field value (get/set) */
+	__u32 fa_extsize;	/* extsize field value (get/set)*/
+	__u32 fa_nextents;	/* nextents field value (get)   */
+	__u32 fa_projid;	/* project identifier (get/set) */
+	__u32 fa_cowextsize;	/* CoW extsize field value (get/set) */
+};
+
+#define FILE_ATTR_SIZE_VER0 24
+#define FILE_ATTR_SIZE_LATEST FILE_ATTR_SIZE_VER0
+
 /*
  * Flags for the fsx_xflags field
  */
diff --git 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
