thodg/libgit2

2017-03-28T10:12:23

fileops: do not overwrite correct error message on mmap When executing `git_futils_mmap_ro_file`, we first try to guess whether the file is mmapable at all. Part of this check is whether the file is too large to be mmaped, which can be true on systems with 32 bit `size_t` types. The check is performed by first getting the file size wtih `git_futils_filesize` and then checking whether the returned size can be represented as `size_t`, returning an error if so. While this test also catches the case where the function returned an error (as `-1` is not representable by `size_t`), we will set the misleading error message "file too large to mmap". But in fact, a negative return value from `git_futils_filesize` will be caused by the inability to fstat the file. Fix the error message by handling negative return values separately and not overwriting the error message in that case.

diff --git a/src/fileops.c b/src/fileops.c
index ad2a988..f9552a5 100644
--- a/src/fileops.c
+++ b/src/fileops.c
@@ -304,7 +304,9 @@ int git_futils_mmap_ro_file(git_map *out, const char *path)
 	if (fd < 0)
 		return fd;
 
-	len = git_futils_filesize(fd);
+	if ((len = git_futils_filesize(fd)) < 0)
+		return -1;
+
 	if (!git__is_sizet(len)) {
 		giterr_set(GITERR_OS, "file `%s` too large to mmap", path);
 		return -1;