1 files changed, 27 insertions, 5 deletions

diff --git a/src/posix.c b/src/posix.c
index debd8d2c8..bf764ae6b 100644
--- a/src/posix.c
+++ b/src/posix.c
@@ -238,6 +238,9 @@ int git__mmap_alignment(size_t *alignment)
 
 int p_mmap(git_map *out, size_t len, int prot, int flags, int fd, off64_t offset)
 {
+	const char *ptr;
+	size_t remaining_len;
+
 	GIT_MMAP_VALIDATE(out, len, prot, flags);
 
 	/* writes cannot be emulated without handling pagefaults since write happens by
@@ -248,15 +251,30 @@ int p_mmap(git_map *out, size_t len, int prot, int flags, int fd, off64_t offset
 		return -1;
 	}
 
+	if (!git__is_ssizet(len)) {
+		errno = EINVAL;
+		return -1;
+	}
+
 	out->len = 0;
 	out->data = git__malloc(len);
 	GIT_ERROR_CHECK_ALLOC(out->data);
 
-	if (!git__is_ssizet(len) ||
-		(p_lseek(fd, offset, SEEK_SET) < 0) ||
-		(p_read(fd, out->data, len) != (ssize_t)len)) {
-		git_error_set(GIT_ERROR_OS, "mmap emulation failed");
-		return -1;
+	remaining_len = len;
+	ptr = (const char *)out->data;
+	while (remaining_len > 0) {
+		ssize_t nb;
+		HANDLE_EINTR(nb, p_pread(fd, (void *)ptr, remaining_len, offset));
+		if (nb <= 0) {
+			git_error_set(GIT_ERROR_OS, "mmap emulation failed");
+			git__free(out->data);
+			out->data = NULL;
+			return -1;
+		}
+
+		ptr += nb;
+		offset += nb;
+		remaining_len -= nb;
 	}
 
 	out->len = len;
@@ -268,6 +286,10 @@ int p_munmap(git_map *map)
 	GIT_ASSERT_ARG(map);
 	git__free(map->data);
 
+	/* Initializing will help debug use-after-free */
+	map->len = 0;
+	map->data = NULL;
+
 	return 0;
 }