Fix cache algorithm loophole

This closes the door for unneccessary calls to cgit_fill_cache().

Noticed by Linus.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

3 files changed, 16 insertions, 11 deletions

diff --git a/cache.c b/cache.c
index b034c48..0ffa502 100644
--- a/cache.c
+++ b/cache.c
@@ -1,64 +1,68 @@
 /* cache.c: cache management
  *
  * Copyright (C) 2006 Lars Hjemli
  *
  * Licensed under GNU General Public License v2
  *   (see COPYING for full license text)
  */
 
 #include "cgit.h"
 
 const int NOLOCK = -1;
 
-int cache_lookup(struct cacheitem *item)
+void cache_prepare(struct cacheitem *item)
 {
         if (!cgit_query_repo) {
                 item->name = xstrdup(fmt("%s/index.html", cgit_cache_root));
                 item->ttl = cgit_cache_root_ttl;
         } else if (!cgit_query_page) {
                 item->name = xstrdup(fmt("%s/%s/index.html", cgit_cache_root, 
                            cgit_query_repo));
                 item->ttl = cgit_cache_repo_ttl;
         } else {
                 item->name = xstrdup(fmt("%s/%s/%s/%s.html", cgit_cache_root, 
                            cgit_query_repo, cgit_query_page, 
                            cgit_querystring));
                 if (cgit_query_has_symref)
                         item->ttl = cgit_cache_dynamic_ttl;
                 else if (cgit_query_has_sha1)
                         item->ttl = cgit_cache_static_ttl;
                 else
                         item->ttl = cgit_cache_repo_ttl;
         }
+}
+
+int cache_exist(struct cacheitem *item)
+{
         if (stat(item->name, &item->st)) {
                 item->st.st_mtime = 0;
                 return 0;
         }
         return 1;
 }
 
 int cache_create_dirs()
 {
         char *path;
 
         if (!cgit_query_repo)
                 return 0;
 
         path = fmt("%s/%s", cgit_cache_root, cgit_query_repo);
         if (mkdir(path, S_IRWXU) && errno!=EEXIST)
                 return 0;
 
         if (cgit_query_page) {
                 path = fmt("%s/%s/%s", cgit_cache_root, cgit_query_repo, 
                            cgit_query_page);
                 if (mkdir(path, S_IRWXU) && errno!=EEXIST)
                         return 0;
         }
         return 1;
 }
 
 int cache_lock(struct cacheitem *item)
 {
         int ret;
         char *lockfile = fmt("%s.lock", item->name);
 
diff --git a/cgit.c b/cgit.c
index 110face..7f14016 100644
--- a/cgit.c
+++ b/cgit.c
@@ -436,73 +436,73 @@ static void cgit_print_repo_page()
                 cgit_print_pageheader(title);
                 htmlf(cgit_lib_error, "Unable to scan repository",
                       strerror(errno));
                 cgit_print_docend();
                 return;
         }
         setenv("GIT_DIR", fmt("%s/%s", cgit_root, cgit_query_repo), 1);
         char *title = fmt("%s - %s", cgit_repo_name, cgit_repo_desc);
         cgit_print_docstart(title);
         cgit_print_pageheader(title);
         if (!cgit_query_page)
                 cgit_print_repo_summary();
         else if (!strcmp(cgit_query_page, "log")) {
                 cgit_print_log(cgit_query_head, 0, 100);
         } else if (!strcmp(cgit_query_page, "view")) {
                 cgit_print_object(cgit_query_sha1);
         }
         cgit_print_docend();
 }
 
 static void cgit_fill_cache(struct cacheitem *item)
 {
         htmlfd = item->fd;
         item->st.st_mtime = time(NULL);
         if (cgit_query_repo)
                 cgit_print_repo_page();
         else
                 cgit_print_repolist();
 }
 
 static void cgit_refresh_cache(struct cacheitem *item)
 {
+        cache_prepare(item);
  top:
-        if (!cache_lookup(item)) {
-                if (cache_lock(item)) {
-                        cgit_fill_cache(item);
-                        cache_unlock(item);
-                } else {
+        if (!cache_exist(item)) {
+                if (!cache_lock(item)) {
                         sched_yield();
                         goto top;
                 }
-        } else if (cache_expired(item)) {
-                if (cache_lock(item)) {
+                if (!cache_exist(item))
                         cgit_fill_cache(item);
-                        cache_unlock(item);
-                }
+                cache_unlock(item);
+        } else if (cache_expired(item) && cache_lock(item)) {
+                if (cache_expired(item))
+                        cgit_fill_cache(item);
+                cache_unlock(item);
         }
 }
 
 static void cgit_print_cache(struct cacheitem *item)
 {
         static char buf[4096];
         ssize_t i;
 
         int fd = open(item->name, O_RDONLY);
         if (fd<0)
                 die("Unable to open cached file %s", item->name);
 
         while((i=read(fd, buf, sizeof(buf))) > 0)
                 write(STDOUT_FILENO, buf, i);
 
         close(fd);
 }
 
 int main(int argc, const char **argv)
 {
         cgit_read_config("/etc/cgitrc", cgit_global_config_cb);
         cgit_querystring = xstrdup(getenv("QUERY_STRING"));
         cgit_parse_query(cgit_querystring, cgit_querystring_cb);
         cgit_refresh_cache(&cacheitem);
         cgit_print_cache(&cacheitem);
         return 0;
 }
diff --git a/cgit.h b/cgit.h
index 1e084d4..3b0994a 100644
--- a/cgit.h
+++ b/cgit.h
@@ -27,38 +27,39 @@ extern int cgit_cache_root_ttl;
 extern int cgit_cache_repo_ttl;
 extern int cgit_cache_dynamic_ttl;
 extern int cgit_cache_static_ttl;
 extern int cgit_cache_max_create_time;
 
 extern char *cgit_repo_name;
 extern char *cgit_repo_desc;
 extern char *cgit_repo_owner;
 
 extern int cgit_query_has_symref;
 extern int cgit_query_has_sha1;
 
 extern char *cgit_querystring;
 extern char *cgit_query_repo;
 extern char *cgit_query_page;
 extern char *cgit_query_head;
 extern char *cgit_query_sha1;
 
 extern int htmlfd;
 
 extern char *fmt(const char *format,...);
 
 extern void html(const char *txt);
 extern void htmlf(const char *format,...);
 extern void html_txt(char *txt);
 extern void html_attr(char *txt);
 extern void html_link_open(char *url, char *title, char *class);
 extern void html_link_close(void);
 
 
 extern int cgit_read_config(const char *filename, configfn fn);
 
-extern int cache_lookup(struct cacheitem *item);
+extern void cache_prepare(struct cacheitem *item);
 extern int cache_lock(struct cacheitem *item);
 extern int cache_unlock(struct cacheitem *item);
+extern int cache_exist(struct cacheitem *item);
 extern int cache_expired(struct cacheitem *item);
 
 #endif /* CGIT_H */