From 6140be90ec70c39fa844741ca3cc807dd0866394 Mon Sep 17 00:00:00 2001 From: Christian Göttsche Date: Fri, 26 Apr 2024 18:20:14 +0200 Subject: fs/xattr: add *at family syscalls MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add the four syscalls setxattrat(), getxattrat(), listxattrat() and removexattrat(). Those can be used to operate on extended attributes, especially security related ones, either relative to a pinned directory or on a file descriptor without read access, avoiding a /proc//fd/ detour, requiring a mounted procfs. One use case will be setfiles(8) setting SELinux file contexts ("security.selinux") without race conditions and without a file descriptor opened with read access requiring SELinux read permission. Use the do_{name}at() pattern from fs/open.c. Pass the value of the extended attribute, its length, and for setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added struct xattr_args to not exceed six syscall arguments and not merging the AT_* and XATTR_* flags. [AV: fixes by Christian Brauner folded in, the entire thing rebased on top of {filename,file}_...xattr() primitives, treatment of empty pathnames regularized. As the result, AT_EMPTY_PATH+NULL handling is cheap, so f...(2) can use it] Signed-off-by: Christian Göttsche Link: https://lore.kernel.org/r/20240426162042.191916-1-cgoettsche@seltendoof.de Reviewed-by: Arnd Bergmann Reviewed-by: Christian Brauner CC: x86@kernel.org CC: linux-alpha@vger.kernel.org CC: linux-kernel@vger.kernel.org CC: linux-arm-kernel@lists.infradead.org CC: linux-ia64@vger.kernel.org CC: linux-m68k@lists.linux-m68k.org CC: linux-mips@vger.kernel.org CC: linux-parisc@vger.kernel.org CC: linuxppc-dev@lists.ozlabs.org CC: linux-s390@vger.kernel.org CC: linux-sh@vger.kernel.org CC: sparclinux@vger.kernel.org CC: linux-fsdevel@vger.kernel.org CC: audit@vger.kernel.org CC: linux-arch@vger.kernel.org CC: linux-api@vger.kernel.org CC: linux-security-module@vger.kernel.org CC: selinux@vger.kernel.org [brauner: slight tweaks] Signed-off-by: Christian Brauner Signed-off-by: Al Viro --- include/asm-generic/audit_change_attr.h | 6 ++++++ include/linux/syscalls.h | 13 +++++++++++++ include/linux/xattr.h | 4 ++++ include/uapi/asm-generic/unistd.h | 11 ++++++++++- include/uapi/linux/xattr.h | 7 +++++++ 5 files changed, 40 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/asm-generic/audit_change_attr.h b/include/asm-generic/audit_change_attr.h index 331670807cf0..cc840537885f 100644 --- a/include/asm-generic/audit_change_attr.h +++ b/include/asm-generic/audit_change_attr.h @@ -11,9 +11,15 @@ __NR_lchown, __NR_fchown, #endif __NR_setxattr, +#ifdef __NR_setxattrat +__NR_setxattrat, +#endif __NR_lsetxattr, __NR_fsetxattr, __NR_removexattr, +#ifdef __NR_removexattrat +__NR_removexattrat, +#endif __NR_lremovexattr, __NR_fremovexattr, #ifdef __NR_fchownat diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 5758104921e6..c6333204d451 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -77,6 +77,7 @@ struct cachestat_range; struct cachestat; struct statmount; struct mnt_id_req; +struct xattr_args; #include #include @@ -338,23 +339,35 @@ asmlinkage long sys_io_uring_register(unsigned int fd, unsigned int op, void __user *arg, unsigned int nr_args); asmlinkage long sys_setxattr(const char __user *path, const char __user *name, const void __user *value, size_t size, int flags); +asmlinkage long sys_setxattrat(int dfd, const char __user *path, unsigned int at_flags, + const char __user *name, + const struct xattr_args __user *args, size_t size); asmlinkage long sys_lsetxattr(const char __user *path, const char __user *name, const void __user *value, size_t size, int flags); asmlinkage long sys_fsetxattr(int fd, const char __user *name, const void __user *value, size_t size, int flags); asmlinkage long sys_getxattr(const char __user *path, const char __user *name, void __user *value, size_t size); +asmlinkage long sys_getxattrat(int dfd, const char __user *path, unsigned int at_flags, + const char __user *name, + struct xattr_args __user *args, size_t size); asmlinkage long sys_lgetxattr(const char __user *path, const char __user *name, void __user *value, size_t size); asmlinkage long sys_fgetxattr(int fd, const char __user *name, void __user *value, size_t size); asmlinkage long sys_listxattr(const char __user *path, char __user *list, size_t size); +asmlinkage long sys_listxattrat(int dfd, const char __user *path, + unsigned int at_flags, + char __user *list, size_t size); asmlinkage long sys_llistxattr(const char __user *path, char __user *list, size_t size); asmlinkage long sys_flistxattr(int fd, char __user *list, size_t size); asmlinkage long sys_removexattr(const char __user *path, const char __user *name); +asmlinkage long sys_removexattrat(int dfd, const char __user *path, + unsigned int at_flags, + const char __user *name); asmlinkage long sys_lremovexattr(const char __user *path, const char __user *name); asmlinkage long sys_fremovexattr(int fd, const char __user *name); diff --git a/include/linux/xattr.h b/include/linux/xattr.h index d20051865800..86b0d47984a1 100644 --- a/include/linux/xattr.h +++ b/include/linux/xattr.h @@ -19,6 +19,10 @@ #include #include +/* List of all open_how "versions". */ +#define XATTR_ARGS_SIZE_VER0 16 /* sizeof first published struct */ +#define XATTR_ARGS_SIZE_LATEST XATTR_ARGS_SIZE_VER0 + struct inode; struct dentry; diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h index 5bf6148cac2b..88dc393c2bca 100644 --- a/include/uapi/asm-generic/unistd.h +++ b/include/uapi/asm-generic/unistd.h @@ -841,8 +841,17 @@ __SYSCALL(__NR_lsm_list_modules, sys_lsm_list_modules) #define __NR_mseal 462 __SYSCALL(__NR_mseal, sys_mseal) +#define __NR_setxattrat 463 +__SYSCALL(__NR_setxattrat, sys_setxattrat) +#define __NR_getxattrat 464 +__SYSCALL(__NR_getxattrat, sys_getxattrat) +#define __NR_listxattrat 465 +__SYSCALL(__NR_listxattrat, sys_listxattrat) +#define __NR_removexattrat 466 +__SYSCALL(__NR_removexattrat, sys_removexattrat) + #undef __NR_syscalls -#define __NR_syscalls 463 +#define __NR_syscalls 467 /* * 32 bit systems traditionally used different diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h index 9463db2dfa9d..9854f9cff3c6 100644 --- a/include/uapi/linux/xattr.h +++ b/include/uapi/linux/xattr.h @@ -11,6 +11,7 @@ */ #include +#include #ifndef _UAPI_LINUX_XATTR_H #define _UAPI_LINUX_XATTR_H @@ -20,6 +21,12 @@ #define XATTR_CREATE 0x1 /* set value, fail if attr already exists */ #define XATTR_REPLACE 0x2 /* set value, fail if attr does not exist */ + +struct xattr_args { + __aligned_u64 __user value; + __u32 size; + __u32 flags; +}; #endif /* Namespaces */ -- cgit v1.2.3