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authorBradford C. Smith <bradford.carl.smith@gmail.com>2007-07-26 17:34:14 (GMT)
committerJunio C Hamano <gitster@pobox.com>2007-07-27 07:02:05 (GMT)
commit5d5a7a67384ad03007eea1f365ee255c02a40fa3 (patch)
tree6064b9f7a5608bcf253066bb4579a415a7d7e4c4 /lockfile.c
parent7ab3cc70a6aad2e4f8ccaa98e5520aa126eaef8f (diff)
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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>
Diffstat (limited to 'lockfile.c')
-rw-r--r--lockfile.c116
1 files changed, 102 insertions, 14 deletions
diff --git a/lockfile.c b/lockfile.c
index 9202472..9a1f64d 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -25,23 +25,111 @@ static void remove_lock_file_on_signal(int signo)
raise(signo);
}
+/*
+ * p = absolute or relative path name
+ *
+ * Return a pointer into p showing the beginning of the last path name
+ * element. If p is empty or the root directory ("/"), just return p.
+ */
+static char *last_path_elm(char *p)
+{
+ /* r starts pointing to null at the end of the string */
+ char *r = strchr(p, '\0');
+
+ if (r == p)
+ return p; /* just return empty string */
+
+ r--; /* back up to last non-null character */
+
+ /* back up past trailing slashes, if any */
+ while (r > p && *r == '/')
+ r--;
+
+ /*
+ * then go backwards until I hit a slash, or the beginning of
+ * the string
+ */
+ while (r > p && *(r-1) != '/')
+ r--;
+ return r;
+}
+
+
+/* We allow "recursive" symbolic links. Only within reason, though */
+#define MAXDEPTH 5
+
+/*
+ * p = path that may be a symlink
+ * s = full size of p
+ *
+ * If p is a symlink, attempt to overwrite p with a path to the real
+ * file or directory (which may or may not exist), following a chain of
+ * symlinks if necessary. Otherwise, leave p unmodified.
+ *
+ * This is a best-effort routine. If an error occurs, p will either be
+ * left unmodified or will name a different symlink in a symlink chain
+ * that started with p's initial contents.
+ *
+ * Always returns p.
+ */
+
+static char *resolve_symlink(char *p, size_t s)
+{
+ int depth = MAXDEPTH;
+
+ while (depth--) {
+ char link[PATH_MAX];
+ int link_len = readlink(p, link, sizeof(link));
+ if (link_len < 0) {
+ /* not a symlink anymore */
+ return p;
+ }
+ else if (link_len < sizeof(link))
+ /* readlink() never null-terminates */
+ link[link_len] = '\0';
+ else {
+ warning("%s: symlink too long", p);
+ return p;
+ }
+
+ if (link[0] == '/') {
+ /* absolute path simply replaces p */
+ if (link_len < s)
+ strcpy(p, link);
+ else {
+ warning("%s: symlink too long", p);
+ return p;
+ }
+ } else {
+ /*
+ * link is a relative path, so I must replace the
+ * last element of p with it.
+ */
+ char *r = (char*)last_path_elm(p);
+ if (r - p + link_len < s)
+ strcpy(r, link);
+ else {
+ warning("%s: symlink too long", p);
+ return p;
+ }
+ }
+ }
+ return p;
+}
+
+
static int lock_file(struct lock_file *lk, const char *path)
{
int fd;
- struct stat st;
-
- if ((!lstat(path, &st)) && S_ISLNK(st.st_mode)) {
- ssize_t sz;
- static char target[PATH_MAX];
- sz = readlink(path, target, sizeof(target));
- if (sz < 0)
- warning("Cannot readlink %s", path);
- else if (target[0] != '/')
- warning("Cannot lock target of relative symlink %s", path);
- else
- path = target;
- }
- sprintf(lk->filename, "%s.lock", path);
+
+ if (strlen(path) >= sizeof(lk->filename)) return -1;
+ strcpy(lk->filename, path);
+ /*
+ * subtract 5 from size to make sure there's room for adding
+ * ".lock" for the lock file name
+ */
+ resolve_symlink(lk->filename, sizeof(lk->filename)-5);
+ strcat(lk->filename, ".lock");
fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
if (0 <= fd) {
if (!lock_file_list) {