[PATCH v6 6/6] fs: introduce file_getattr and file_setattr syscalls
From: Andrey Albershteyn <hidden>
Date: 2025-06-30 16:20:41
Also in:
linux-fsdevel, linux-xfs, lkml, selinux
Subsystem:
abi/api, alpha port, arm port, arm64 port (aarch64 architecture), filesystems (vfs and infrastructure), generic include/asm header files, linux for powerpc (32-bit and 64-bit), m68k architecture, microblaze architecture, mips, parisc architecture, s390 architecture, sparc + ultrasparc (sparc/sparc64), superh, tensilica xtensa port (xtensa), the rest, x86 architecture (32-bit and 64-bit), x86 entry code · Maintainers:
Richard Henderson, Matt Turner, Magnus Lindholm, Russell King, Catalin Marinas, Will Deacon, Alexander Viro, Christian Brauner, Arnd Bergmann, Madhavan Srinivasan, Michael Ellerman, Geert Uytterhoeven, Michal Simek, Thomas Bogendoerfer, "James E.J. Bottomley", Helge Deller, Heiko Carstens, Vasily Gorbik, Alexander Gordeev, "David S. Miller", Andreas Larsson, Yoshinori Sato, Rich Felker, John Paul Adrian Glaubitz, Chris Zankel, Max Filippov, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski
From: Andrey Albershteyn <redacted> 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