setup: sanity check file size in read_gitfile_gently

read_gitfile_gently will allocate a buffer to fit the entire file that
should be read. Add a sanity check of the file size before opening to
avoid allocating a potentially huge amount of memory if we come across
a large file that someone happened to name ".git". The limit is set to
a sufficiently unreasonable size that should never be exceeded by a
genuine .git file.

Signed-off-by: Erik Elfström <erik.elfstrom@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/cache.h b/cache.h
index 25578cbf3cd29ca2a4f4fc2a4423eb8136cff164..858d9b368801a19ccab9c91c719e3b15680b7bd5 100644 (file)
--- a/cache.h
+++ b/cache.h
@@ -454,6 +454,7 @@ extern const char *get_git_work_tree(void);
 #define READ_GITFILE_ERR_INVALID_FORMAT 5
 #define READ_GITFILE_ERR_NO_PATH 6
 #define READ_GITFILE_ERR_NOT_A_REPO 7
+#define READ_GITFILE_ERR_TOO_LARGE 8
 extern const char *read_gitfile_gently(const char *path, int *return_error_code);
 #define read_gitfile(path) read_gitfile_gently((path), NULL)
 extern const char *resolve_gitdir(const char *suspect);

diff --git a/setup.c b/setup.c
index 4748b6338d8fe338d4e001f9e9587ba349ab05a4..a03ca94234e944570cceb5d3e556c214cf1f387a 100644 (file)
--- a/setup.c
+++ b/setup.c
@@ -414,6 +414,7 @@ static void update_linked_gitdir(const char *gitfile, const char *gitdir)
  */
 const char *read_gitfile_gently(const char *path, int *return_error_code)
 {
+       const int max_file_size = 1 << 20;  /* 1MB */
        int error_code = 0;
        char *buf = NULL;
        char *dir = NULL;
@@ -430,6 +431,10 @@ const char *read_gitfile_gently(const char *path, int *return_error_code)
                error_code = READ_GITFILE_ERR_NOT_A_FILE;
                goto cleanup_return;
        }
+       if (st.st_size > max_file_size) {
+               error_code = READ_GITFILE_ERR_TOO_LARGE;
+               goto cleanup_return;
+       }
        fd = open(path, O_RDONLY);
        if (fd < 0) {
                error_code = READ_GITFILE_ERR_OPEN_FAILED;
@@ -489,6 +494,8 @@ const char *read_gitfile_gently(const char *path, int *return_error_code)
                        return NULL;
                case READ_GITFILE_ERR_OPEN_FAILED:
                        die_errno("Error opening '%s'", path);
+               case READ_GITFILE_ERR_TOO_LARGE:
+                       die("Too large to be a .git file: '%s'", path);
                case READ_GITFILE_ERR_READ_FAILED:
                        die("Error reading %s", path);
                case READ_GITFILE_ERR_INVALID_FORMAT: