/* rename.c -- rename a file, preserving symlinks.
- Copyright (C) 1999-2016 Free Software Foundation, Inc.
+ Copyright (C) 1999-2021 Free Software Foundation, Inc.
This file is part of GNU Binutils.
#endif
#endif
-/* Rename FROM to TO, copying if TO is a link.
- Return 0 if ok, -1 if error. */
+#if !defined (_WIN32) || defined (__CYGWIN32__)
+/* Try to preserve the permission bits and ownership of an existing file when
+ rename overwrites it. FD is the file being renamed and TARGET_STAT has the
+ status of the file that was overwritten. */
+static void
+try_preserve_permissions (int fd, struct stat *target_stat)
+{
+ struct stat from_stat;
+ int ret = 0;
+
+ if (fstat (fd, &from_stat) != 0)
+ return;
+
+ int from_mode = from_stat.st_mode & 0777;
+ int to_mode = target_stat->st_mode & 0777;
+
+ /* Fix up permissions before we potentially lose ownership with fchown.
+ Clear the setxid bits because in case the fchown below fails then we don't
+ want to end up with a sxid file owned by the invoking user. If the user
+ hasn't changed or if fchown succeeded, we add back the sxid bits at the
+ end. */
+ if (from_mode != to_mode)
+ fchmod (fd, to_mode);
+
+ /* Fix up ownership, this will clear the setxid bits. */
+ if (from_stat.st_uid != target_stat->st_uid
+ || from_stat.st_gid != target_stat->st_gid)
+ ret = fchown (fd, target_stat->st_uid, target_stat->st_gid);
+
+ /* Fix up the sxid bits if either the fchown wasn't needed or it
+ succeeded. */
+ if (ret == 0)
+ fchmod (fd, target_stat->st_mode & 07777);
+}
+#endif
+
+/* Rename FROM to TO, copying if TO is either a link or is not a regular file.
+ FD is an open file descriptor pointing to FROM that we can use to safely fix
+ up permissions of the file after renaming. TARGET_STAT has the file status
+ that is used to fix up permissions and timestamps after rename. Return 0 if
+ ok, -1 if error and FD is closed before returning. */
int
-smart_rename (const char *from, const char *to, int preserve_dates ATTRIBUTE_UNUSED)
+smart_rename (const char *from, const char *to, int fd ATTRIBUTE_UNUSED,
+ struct stat *target_stat ATTRIBUTE_UNUSED,
+ int preserve_dates ATTRIBUTE_UNUSED)
{
- bfd_boolean exists;
- struct stat s;
int ret = 0;
-
- exists = lstat (to, &s) == 0;
+ bfd_boolean exists = target_stat != NULL;
#if defined (_WIN32) && !defined (__CYGWIN32__)
/* Win32, unlike unix, will not erase `to' in `rename(from, to)' but
unlink (from);
}
#else
- /* Use rename only if TO is not a symbolic link and has
- only one hard link, and we have permission to write to it. */
+ /* Avoid a full copy and use rename if we can fix up permissions of the
+ file after renaming, i.e.:
+
+ - TO is not a symbolic link
+ - TO is a regular file with only one hard link
+ - We have permission to write to TO
+ - FD is available to safely fix up permissions to be the same as the file
+ we overwrote with the rename.
+
+ Note though that the actual file on disk that TARGET_STAT describes may
+ have changed and we're only trying to preserve the status we know about.
+ At no point do we try to interact with the new file changes, so there can
+ only be two outcomes, i.e. either the external file change survives
+ without knowledge of our change (if it happens after the rename syscall)
+ or our rename and permissions fixup survive without any knowledge of the
+ external change. */
if (! exists
- || (!S_ISLNK (s.st_mode)
- && S_ISREG (s.st_mode)
- && (s.st_mode & S_IWUSR)
- && s.st_nlink == 1)
+ || (fd >= 0
+ && !S_ISLNK (target_stat->st_mode)
+ && S_ISREG (target_stat->st_mode)
+ && (target_stat->st_mode & S_IWUSR)
+ && target_stat->st_nlink == 1)
)
{
ret = rename (from, to);
if (ret == 0)
{
if (exists)
- {
- /* Try to preserve the permission bits and ownership of
- TO. First get the mode right except for the setuid
- bit. Then change the ownership. Then fix the setuid
- bit. We do the chmod before the chown because if the
- chown succeeds, and we are a normal user, we won't be
- able to do the chmod afterward. We don't bother to
- fix the setuid bit first because that might introduce
- a fleeting security problem, and because the chown
- will clear the setuid bit anyhow. We only fix the
- setuid bit if the chown succeeds, because we don't
- want to introduce an unexpected setuid file owned by
- the user running objcopy. */
- chmod (to, s.st_mode & 0777);
- if (chown (to, s.st_uid, s.st_gid) >= 0)
- chmod (to, s.st_mode & 07777);
- }
+ try_preserve_permissions (fd, target_stat);
}
else
{
non_fatal (_("unable to copy file '%s'; reason: %s"), to, strerror (errno));
if (preserve_dates)
- set_times (to, &s);
+ set_times (to, target_stat);
unlink (from);
}
+ if (fd >= 0)
+ close (fd);
#endif /* _WIN32 && !__CYGWIN32__ */
return ret;
projects / thirdparty / binutils-gdb.git / blobdiff