fully resolve symlinks when creating lockfiles
Make the code for resolving symlinks in lockfile.c more robust as follows: 1. Handle relative symlinks 2. recursively resolve symlink chains up to 5 [jc: removed lstat/stat calls to do things stupid way] Signed-off-by: Bradford C. Smith <bradford.carl.smith@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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114
lockfile.c
114
lockfile.c
@ -25,23 +25,111 @@ static void remove_lock_file_on_signal(int signo)
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raise(signo);
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raise(signo);
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}
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}
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/*
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* p = absolute or relative path name
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*
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* Return a pointer into p showing the beginning of the last path name
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* element. If p is empty or the root directory ("/"), just return p.
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*/
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static char *last_path_elm(char *p)
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{
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/* r starts pointing to null at the end of the string */
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char *r = strchr(p, '\0');
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if (r == p)
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return p; /* just return empty string */
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r--; /* back up to last non-null character */
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/* back up past trailing slashes, if any */
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while (r > p && *r == '/')
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r--;
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/*
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* then go backwards until I hit a slash, or the beginning of
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* the string
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*/
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while (r > p && *(r-1) != '/')
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r--;
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return r;
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}
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/* We allow "recursive" symbolic links. Only within reason, though */
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#define MAXDEPTH 5
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/*
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* p = path that may be a symlink
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* s = full size of p
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*
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* If p is a symlink, attempt to overwrite p with a path to the real
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* file or directory (which may or may not exist), following a chain of
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* symlinks if necessary. Otherwise, leave p unmodified.
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*
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* This is a best-effort routine. If an error occurs, p will either be
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* left unmodified or will name a different symlink in a symlink chain
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* that started with p's initial contents.
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*
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* Always returns p.
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*/
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static char *resolve_symlink(char *p, size_t s)
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{
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int depth = MAXDEPTH;
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while (depth--) {
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char link[PATH_MAX];
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int link_len = readlink(p, link, sizeof(link));
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if (link_len < 0) {
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/* not a symlink anymore */
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return p;
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}
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else if (link_len < sizeof(link))
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/* readlink() never null-terminates */
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link[link_len] = '\0';
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else {
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warning("%s: symlink too long", p);
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return p;
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}
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if (link[0] == '/') {
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/* absolute path simply replaces p */
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if (link_len < s)
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strcpy(p, link);
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else {
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warning("%s: symlink too long", p);
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return p;
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}
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} else {
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/*
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* link is a relative path, so I must replace the
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* last element of p with it.
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*/
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char *r = (char*)last_path_elm(p);
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if (r - p + link_len < s)
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strcpy(r, link);
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else {
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warning("%s: symlink too long", p);
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return p;
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}
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}
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}
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return p;
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}
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static int lock_file(struct lock_file *lk, const char *path)
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static int lock_file(struct lock_file *lk, const char *path)
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{
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{
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int fd;
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int fd;
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struct stat st;
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if ((!lstat(path, &st)) && S_ISLNK(st.st_mode)) {
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if (strlen(path) >= sizeof(lk->filename)) return -1;
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ssize_t sz;
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strcpy(lk->filename, path);
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static char target[PATH_MAX];
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/*
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sz = readlink(path, target, sizeof(target));
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* subtract 5 from size to make sure there's room for adding
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if (sz < 0)
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* ".lock" for the lock file name
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warning("Cannot readlink %s", path);
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*/
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else if (target[0] != '/')
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resolve_symlink(lk->filename, sizeof(lk->filename)-5);
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warning("Cannot lock target of relative symlink %s", path);
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strcat(lk->filename, ".lock");
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else
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path = target;
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}
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sprintf(lk->filename, "%s.lock", path);
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fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
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fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
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if (0 <= fd) {
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if (0 <= fd) {
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if (!lock_file_list) {
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if (!lock_file_list) {
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