ld.so: Check for new cache format first and enhance corruption check

Now that ldconfig defaults to the new format (only), check for it
first.  Also apply the corruption check added in commit 2954daf00bb4d
("Add more checks for valid ld.so.cache file (bug 18093)") to the
new-format-only case.

Suggested-by: Josh Triplett <josh@joshtriplett.org>

diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index 3eedd9afcf41cea8714f2db8c46988d94fed5c2c..93d185e788b0866b231526737bfdb024f38c846d 100644 (file)
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -199,15 +199,25 @@ _dl_load_cache_lookup (const char *name)
                                               PROT_READ);
 
       /* We can handle three different cache file formats here:
+        - only the new format
         - the old libc5/glibc2.0/2.1 format
         - the old format with the new format in it
-        - only the new format
         The following checks if the cache contains any of these formats.  */
-      if (file != MAP_FAILED && cachesize > sizeof *cache
-         && memcmp (file, CACHEMAGIC, sizeof CACHEMAGIC - 1) == 0
+      if (file != MAP_FAILED && cachesize > sizeof *cache_new
+         && memcmp (file, CACHEMAGIC_VERSION_NEW,
+                    sizeof CACHEMAGIC_VERSION_NEW - 1) == 0
          /* Check for corruption, avoiding overflow.  */
-         && ((cachesize - sizeof *cache) / sizeof (struct file_entry)
-             >= ((struct cache_file *) file)->nlibs))
+         && ((cachesize - sizeof *cache_new) / sizeof (struct file_entry_new)
+             >= ((struct cache_file_new *) file)->nlibs))
+       {
+         cache_new = file;
+         cache = file;
+       }
+      else if (file != MAP_FAILED && cachesize > sizeof *cache
+              && memcmp (file, CACHEMAGIC, sizeof CACHEMAGIC - 1) == 0
+              /* Check for corruption, avoiding overflow.  */
+              && ((cachesize - sizeof *cache) / sizeof (struct file_entry)
+                  >= ((struct cache_file *) file)->nlibs))
        {
          size_t offset;
          /* Looks ok.  */
@@ -223,13 +233,6 @@ _dl_load_cache_lookup (const char *name)
                         sizeof CACHEMAGIC_VERSION_NEW - 1) != 0)
            cache_new = (void *) -1;
        }
-      else if (file != MAP_FAILED && cachesize > sizeof *cache_new
-              && memcmp (file, CACHEMAGIC_VERSION_NEW,
-                         sizeof CACHEMAGIC_VERSION_NEW - 1) == 0)
-       {
-         cache_new = file;
-         cache = file;
-       }
       else
        {
          if (file != MAP_FAILED)