/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include #include #include #include "alloc-util.h" #include "errno-util.h" #include "fd-util.h" #include "macro.h" #include "missing_syscall.h" #include "sparse-endian.h" #include "stat-util.h" #include "stdio-util.h" #include "string-util.h" #include "time-util.h" #include "xattr-util.h" int getxattr_at_malloc( int fd, const char *path, const char *name, int flags, char **ret) { _cleanup_close_ int opened_fd = -EBADF; unsigned n_attempts = 7; bool by_procfs = false; size_t l = 100; assert(fd >= 0 || fd == AT_FDCWD); assert(name); assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0); assert(ret); /* So, this is single function that does what getxattr()/lgetxattr()/fgetxattr() does, but in one go, * and with additional bells and whistles. Specifically: * * 1. This works on O_PATH fds (which fgetxattr() does not) * 2. Provides full openat()-style semantics, i.e. by-fd, by-path and combination thereof * 3. As extension to openat()-style semantics implies AT_EMPTY_PATH if path is NULL. * 4. Does a malloc() loop, automatically sizing the allocation * 5. NUL-terminates the returned buffer (for safety) */ if (!path) /* If path is NULL, imply AT_EMPTY_PATH. – But if it's "", don't — for safety reasons. */ flags |= AT_EMPTY_PATH; if (isempty(path)) { if (!FLAGS_SET(flags, AT_EMPTY_PATH)) return -EINVAL; if (fd == AT_FDCWD) /* Both unspecified? Then operate on current working directory */ path = "."; else path = NULL; } else if (fd != AT_FDCWD) { /* If both have been specified, then we go via O_PATH */ opened_fd = openat(fd, path, O_PATH|O_CLOEXEC|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : O_NOFOLLOW)); if (opened_fd < 0) return -errno; fd = opened_fd; path = NULL; by_procfs = true; /* fgetxattr() is not going to work, go via /proc/ link right-away */ } for (;;) { _cleanup_free_ char *v = NULL; ssize_t n; if (n_attempts == 0) /* If someone is racing against us, give up eventually */ return -EBUSY; n_attempts--; v = new0(char, l+1); if (!v) return -ENOMEM; l = MALLOC_ELEMENTSOF(v) - 1; if (path) n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? getxattr(path, name, v, l) : lgetxattr(path, name, v, l); else n = by_procfs ? getxattr(FORMAT_PROC_FD_PATH(fd), name, v, l) : fgetxattr(fd, name, v, l); if (n < 0) { if (errno == EBADF) { if (by_procfs || path) return -EBADF; by_procfs = true; /* Might be an O_PATH fd, try again via /proc/ link */ continue; } if (errno != ERANGE) return -errno; } else { v[n] = 0; /* NUL terminate */ *ret = TAKE_PTR(v); return (int) n; } if (path) n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? getxattr(path, name, NULL, 0) : lgetxattr(path, name, NULL, 0); else n = by_procfs ? getxattr(FORMAT_PROC_FD_PATH(fd), name, NULL, 0) : fgetxattr(fd, name, NULL, 0); if (n < 0) return -errno; if (n > INT_MAX) /* We couldn't return this as 'int' anymore */ return -E2BIG; l = (size_t) n; } } static int parse_crtime(le64_t le, usec_t *usec) { uint64_t u; assert(usec); u = le64toh(le); if (IN_SET(u, 0, UINT64_MAX)) return -EIO; *usec = (usec_t) u; return 0; } int fd_getcrtime_at( int fd, const char *path, int flags, usec_t *ret) { _cleanup_free_ le64_t *le = NULL; STRUCT_STATX_DEFINE(sx); usec_t a, b; int r; assert(fd >= 0 || fd == AT_FDCWD); assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0); assert(ret); if (!path) flags |= AT_EMPTY_PATH; /* So here's the deal: the creation/birth time (crtime/btime) of a file is a relatively newly supported concept * on Linux (or more strictly speaking: a concept that only recently got supported in the API, it was * implemented on various file systems on the lower level since a while, but never was accessible). However, we * needed a concept like that for vaccuuming algorithms and such, hence we emulated it via a user xattr for a * long time. Starting with Linux 4.11 there's statx() which exposes the timestamp to userspace for the first * time, where it is available. Thius function will read it, but it tries to keep some compatibility with older * systems: we try to read both the crtime/btime and the xattr, and then use whatever is older. After all the * concept is useful for determining how "old" a file really is, and hence using the older of the two makes * most sense. */ if (statx(fd, strempty(path), (flags & ~AT_SYMLINK_FOLLOW)|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : AT_SYMLINK_NOFOLLOW)|AT_STATX_DONT_SYNC, STATX_BTIME, &sx) >= 0 && (sx.stx_mask & STATX_BTIME) && sx.stx_btime.tv_sec != 0) a = (usec_t) sx.stx_btime.tv_sec * USEC_PER_SEC + (usec_t) sx.stx_btime.tv_nsec / NSEC_PER_USEC; else a = USEC_INFINITY; r = getxattr_at_malloc(fd, path, "user.crtime_usec", flags, (char**) &le); if (r >= 0) { if (r != sizeof(*le)) r = -EIO; else r = parse_crtime(*le, &b); } if (r < 0) { if (a != USEC_INFINITY) { *ret = a; return 0; } return r; } if (a != USEC_INFINITY) *ret = MIN(a, b); else *ret = b; return 0; } int fd_setcrtime(int fd, usec_t usec) { le64_t le; assert(fd >= 0); if (!timestamp_is_set(usec)) usec = now(CLOCK_REALTIME); le = htole64((uint64_t) usec); return RET_NERRNO(fsetxattr(fd, "user.crtime_usec", &le, sizeof(le), 0)); } int listxattr_at_malloc( int fd, const char *path, int flags, char **ret) { _cleanup_close_ int opened_fd = -EBADF; bool by_procfs = false; unsigned n_attempts = 7; size_t l = 100; assert(fd >= 0 || fd == AT_FDCWD); assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0); assert(ret); /* This is to listxattr()/llistattr()/flistattr() what getxattr_at_malloc() is to getxattr()/… */ if (!path) /* If path is NULL, imply AT_EMPTY_PATH. – But if it's "", don't. */ flags |= AT_EMPTY_PATH; if (isempty(path)) { if (!FLAGS_SET(flags, AT_EMPTY_PATH)) return -EINVAL; if (fd == AT_FDCWD) /* Both unspecified? Then operate on current working directory */ path = "."; else path = NULL; } else if (fd != AT_FDCWD) { /* If both have been specified, then we go via O_PATH */ opened_fd = openat(fd, path, O_PATH|O_CLOEXEC|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : O_NOFOLLOW)); if (opened_fd < 0) return -errno; fd = opened_fd; path = NULL; by_procfs = true; } for (;;) { _cleanup_free_ char *v = NULL; ssize_t n; if (n_attempts == 0) /* If someone is racing against us, give up eventually */ return -EBUSY; n_attempts--; v = new(char, l+1); if (!v) return -ENOMEM; l = MALLOC_ELEMENTSOF(v) - 1; if (path) n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? listxattr(path, v, l) : llistxattr(path, v, l); else n = by_procfs ? listxattr(FORMAT_PROC_FD_PATH(fd), v, l) : flistxattr(fd, v, l); if (n < 0) { if (errno == EBADF) { if (by_procfs || path) return -EBADF; by_procfs = true; /* Might be an O_PATH fd, try again via /proc/ link */ continue; } if (errno != ERANGE) return -errno; } else { v[n] = 0; /* NUL terminate */ *ret = TAKE_PTR(v); return (int) n; } if (path) n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? listxattr(path, NULL, 0) : llistxattr(path, NULL, 0); else n = by_procfs ? listxattr(FORMAT_PROC_FD_PATH(fd), NULL, 0) : flistxattr(fd, NULL, 0); if (n < 0) return -errno; if (n > INT_MAX) /* We couldn't return this as 'int' anymore */ return -E2BIG; l = (size_t) n; } }