[PATCH 1/3] libkmod: add finit_module logic

[Kees Cook <keescook@xxxxxxxxxxxx>]

When a module is being loaded directly from disk (no compression,
etc), pass the file descriptor to the new finit_module() syscall. If
finit_module is exported by glibc, use it. Otherwise, manually make
the syscall on architectures where it is known to exist.
---
 libkmod/libkmod-file.c    |   16 +++++++++++++++-
 libkmod/libkmod-module.c  |   18 ++++++++++++++++++
 libkmod/libkmod-private.h |    2 ++
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/libkmod/libkmod-file.c b/libkmod/libkmod-file.c
index ced20a8..76585f5 100644
--- a/libkmod/libkmod-file.c
+++ b/libkmod/libkmod-file.c
@@ -52,6 +52,7 @@ struct kmod_file {
 	gzFile gzf;
 #endif
 	int fd;
+	int direct;
 	off_t size;
 	void *memory;
 	const struct file_ops *ops;
@@ -254,9 +255,11 @@ static int load_reg(struct kmod_file *file)
 		return -errno;
 
 	file->size = st.st_size;
-	file->memory = mmap(0, file->size, PROT_READ, MAP_PRIVATE, file->fd, 0);
+	file->memory = mmap(NULL, file->size, PROT_READ, MAP_PRIVATE,
+			    file->fd, 0);
 	if (file->memory == MAP_FAILED)
 		return -errno;
+	file->direct = 1;
 	return 0;
 }
 
@@ -300,6 +303,7 @@ struct kmod_file *kmod_file_open(const struct kmod_ctx *ctx,
 			magic_size_max = itr->magic_size;
 	}
 
+	file->direct = 0;
 	if (magic_size_max > 0) {
 		char *buf = alloca(magic_size_max + 1);
 		ssize_t sz;
@@ -353,6 +357,16 @@ off_t kmod_file_get_size(const struct kmod_file *file)
 	return file->size;
 }
 
+int kmod_file_get_direct(const struct kmod_file *file)
+{
+	return file->direct;
+}
+
+int kmod_file_get_fd(const struct kmod_file *file)
+{
+	return file->fd;
+}
+
 void kmod_file_unref(struct kmod_file *file)
 {
 	if (file->elf)
diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
index b1d40b1..5a9473a 100644
--- a/libkmod/libkmod-module.c
+++ b/libkmod/libkmod-module.c
@@ -33,6 +33,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/mman.h>
+#include <sys/syscall.h>
 #include <sys/wait.h>
 #include <string.h>
 #include <fnmatch.h>
@@ -763,6 +764,14 @@ KMOD_EXPORT int kmod_module_remove_module(struct kmod_module *mod,
 
 extern long init_module(const void *mem, unsigned long len, const char *args);
 
+#ifndef __NR_finit_module
+# define __NR_finit_module -1
+#endif
+static inline int finit_module(int fd, const char *uargs, int flags)
+{
+   return syscall(__NR_finit_module, fd, uargs, flags);
+}
+
 /**
  * kmod_module_insert_module:
  * @mod: kmod module
@@ -803,6 +812,14 @@ KMOD_EXPORT int kmod_module_insert_module(struct kmod_module *mod,
 		return err;
 	}
 
+	if (kmod_file_get_direct(file)) {
+		err = finit_module(kmod_file_get_fd(file), args,
+				   flags & (KMOD_INSERT_FORCE_VERMAGIC |
+					    KMOD_INSERT_FORCE_MODVERSION));
+		if (err == 0 || errno != ENOSYS)
+			goto init_finished;
+	}
+
 	size = kmod_file_get_size(file);
 	mem = kmod_file_get_contents(file);
 
@@ -829,6 +846,7 @@ KMOD_EXPORT int kmod_module_insert_module(struct kmod_module *mod,
 	}
 
 	err = init_module(mem, size, args);
+init_finished:
 	if (err < 0) {
 		err = -errno;
 		INFO(mod->ctx, "Failed to insert module '%s': %m\n", path);
diff --git a/libkmod/libkmod-private.h b/libkmod/libkmod-private.h
index b472c62..c765003 100644
--- a/libkmod/libkmod-private.h
+++ b/libkmod/libkmod-private.h
@@ -142,6 +142,8 @@ struct kmod_file *kmod_file_open(const struct kmod_ctx *ctx, const char *filenam
 struct kmod_elf *kmod_file_get_elf(struct kmod_file *file) __attribute__((nonnull(1)));
 void *kmod_file_get_contents(const struct kmod_file *file) _must_check_ __attribute__((nonnull(1)));
 off_t kmod_file_get_size(const struct kmod_file *file) _must_check_ __attribute__((nonnull(1)));
+int kmod_file_get_direct(const struct kmod_file *file) _must_check_ __attribute__((nonnull(1)));
+int kmod_file_get_fd(const struct kmod_file *file) _must_check_ __attribute__((nonnull(1)));
 void kmod_file_unref(struct kmod_file *file) __attribute__((nonnull(1)));
 
 /* libkmod-elf.c */
-- 
1.7.9.5

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