From efeb864cb547a2cbf96dc0053a8bdb4d9190b364 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 12 Jun 2024 05:50:45 +0200 Subject: Merging upstream version 256. Signed-off-by: Daniel Baumann --- src/basic/tmpfile-util.c | 52 ++++++------------------------------------------ 1 file changed, 6 insertions(+), 46 deletions(-) (limited to 'src/basic/tmpfile-util.c') diff --git a/src/basic/tmpfile-util.c b/src/basic/tmpfile-util.c index e77ca94..3a3f7dc 100644 --- a/src/basic/tmpfile-util.c +++ b/src/basic/tmpfile-util.c @@ -330,28 +330,7 @@ int fopen_tmpfile_linkable(const char *target, int flags, char **ret_path, FILE return 0; } -static int link_fd(int fd, int newdirfd, const char *newpath) { - int r; - - assert(fd >= 0); - assert(newdirfd >= 0 || newdirfd == AT_FDCWD); - assert(newpath); - - /* Try symlinking via /proc/fd/ first. */ - r = RET_NERRNO(linkat(AT_FDCWD, FORMAT_PROC_FD_PATH(fd), newdirfd, newpath, AT_SYMLINK_FOLLOW)); - if (r != -ENOENT) - return r; - - /* Fall back to symlinking via AT_EMPTY_PATH as fallback (this requires CAP_DAC_READ_SEARCH and a - * more recent kernel, but does not require /proc/ mounted) */ - if (proc_mounted() != 0) - return r; - - return RET_NERRNO(linkat(fd, "", newdirfd, newpath, AT_EMPTY_PATH)); -} - int link_tmpfile_at(int fd, int dir_fd, const char *path, const char *target, LinkTmpfileFlags flags) { - _cleanup_free_ char *tmp = NULL; int r; assert(fd >= 0); @@ -370,33 +349,14 @@ int link_tmpfile_at(int fd, int dir_fd, const char *path, const char *target, Li r = RET_NERRNO(renameat(dir_fd, path, dir_fd, target)); else r = rename_noreplace(dir_fd, path, dir_fd, target); - if (r < 0) - return r; } else { - - r = link_fd(fd, dir_fd, target); - if (r != -EEXIST || !FLAGS_SET(flags, LINK_TMPFILE_REPLACE)) - return r; - - /* So the target already exists and we were asked to replace it. That sucks a bit, since the kernel's - * linkat() logic does not allow that. We work-around this by linking the file to a random name - * first, and then renaming that to the final name. This reintroduces the race O_TMPFILE kinda is - * trying to fix, but at least the vulnerability window (i.e. where the file is linked into the file - * system under a temporary name) is very short. */ - - r = tempfn_random(target, NULL, &tmp); - if (r < 0) - return r; - - if (link_fd(fd, dir_fd, tmp) < 0) - return -EEXIST; /* propagate original error */ - - r = RET_NERRNO(renameat(dir_fd, tmp, dir_fd, target)); - if (r < 0) { - (void) unlinkat(dir_fd, tmp, 0); - return r; - } + if (FLAGS_SET(flags, LINK_TMPFILE_REPLACE)) + r = linkat_replace(fd, /* oldpath= */ NULL, dir_fd, target); + else + r = link_fd(fd, dir_fd, target); } + if (r < 0) + return r; if (FLAGS_SET(flags, LINK_TMPFILE_SYNC)) { r = fsync_full(fd); -- cgit v1.2.3