Fix handling of mmap failure and mapping empty files

Check the return value of mmap() correctly.

Empty files cannot be mmap'd so we implement some
work around code for that.

https://bugs.freedesktop.org/show_bug.cgi?id=74773

Signed-off-by: Stef Walter <stef@thewalter.net>

diff --git a/common/compat.c b/common/compat.c
index 9aa556a4f6c09d752d30f61227ed35b305103977..f5b88ecda47a0061effbb691e1be85e277b8f8a6 100644 (file)
--- a/common/compat.c
+++ b/common/compat.c
@@ -216,9 +216,15 @@ p11_mmap_open (const char *path,
                return NULL;
        }
 
+       if (sb->st_size == 0) {
+               *data = "";
+               *size = 0;
+               return map;
+       }
+
        map->size = sb->st_size;
        map->data = mmap (NULL, map->size, PROT_READ, MAP_PRIVATE, map->fd, 0);
-       if (map->data == NULL) {
+       if (map->data == MAP_FAILED) {
                close (map->fd);
                free (map);
                return NULL;
@@ -232,7 +238,8 @@ p11_mmap_open (const char *path,
 void
 p11_mmap_close (p11_mmap *map)
 {
-       munmap (map->data, map->size);
+       if (map->size)
+               munmap (map->data, map->size);
        close (map->fd);
        free (map);
 }

diff --git a/common/tests/test-compat.c b/common/tests/test-compat.c
index 872170d43e7eed1dc4359e50642fc51c249e9769..42471ae272d0047c0848422f06c27996a4f67351 100644 (file)
--- a/common/tests/test-compat.c
+++ b/common/tests/test-compat.c
@@ -83,6 +83,22 @@ test_getauxval (void)
        free (path);
 }
 
+static void
+test_mmap (void)
+{
+       p11_mmap *map;
+       void *data;
+       size_t size;
+       char file[] = "emptyfileXXXXXX";
+       int fd = mkstemp (file);
+       close (fd);
+       /* mmap on empty file should work */
+       map = p11_mmap_open (file, NULL, &data, &size);
+       unlink (file);
+       assert_ptr_not_null (map);
+       p11_mmap_close (map);
+}
+
 #endif /* OS_UNIX */
 
 int
@@ -95,6 +111,7 @@ main (int argc,
        if (!getenv ("FAKED_MODE")) {
                p11_test (test_getauxval, "/compat/getauxval");
        }
+       p11_test (test_mmap, "/compat/mmap");
 #endif
        return p11_test_run (argc, argv);
 }