[PATCH v3 3/4] add kexec_cmdline used to ima

[Prakhar Srivastava <prsriva02@gmail.com>]

From: Prakhar Srivastava <prsriva02@gmail.com>

prepend the kernel file name to kexec_cmdline 
before measuring the buffer.

Signed-off-by: Prakhar Srivastava <prsriva02@gmail.com>
---
 kernel/kexec_core.c | 57 +++++++++++++++++++++++++++++++++++++++++++++
 kernel/kexec_file.c | 14 +++++++++++
 2 files changed, 71 insertions(+)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index d7140447be75..4667f03d406e 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1213,3 +1213,60 @@ void __weak arch_kexec_protect_crashkres(void)
 
 void __weak arch_kexec_unprotect_crashkres(void)
 {}
+
+/**
+ * kexec_cmdline_prepend_img_name - prepare the buffer with cmdline
+ * that needs to be measured
+ * @outbuf - out buffer that contains the formated string
+ * @kernel_fd - the file identifier for the kerenel image
+ * @cmdline_ptr - ptr to the cmdline buffer
+ * @cmdline_len - len of the buffer.
+ *
+ * This generates a buffer in the format Kerenelfilename::cmdline
+ *
+ * On success return 0.
+ * On failure return -EINVAL.
+ */
+int kexec_cmdline_prepend_img_name(char **outbuf, int kernel_fd,
+				const char *cmdline_ptr,
+				unsigned long cmdline_len)
+{
+	int ret = -EINVAL;
+	struct fd f = {};
+	int size = 0;
+	char *buf = NULL;
+	char delimiter[] = "::";
+
+	if (!outbuf || !cmdline_ptr)
+		goto out;
+
+	f = fdget(kernel_fd);
+	if (!f.file)
+		goto out;
+
+	size = (f.file->f_path.dentry->d_name.len + cmdline_len - 1+
+			ARRAY_SIZE(delimiter)) - 1;
+
+	buf = kzalloc(size, GFP_KERNEL);
+	if (!buf)
+		goto out;
+
+	memcpy(buf, f.file->f_path.dentry->d_name.name,
+		f.file->f_path.dentry->d_name.len);
+	memcpy(buf + f.file->f_path.dentry->d_name.len,
+		delimiter, ARRAY_SIZE(delimiter) - 1);
+	memcpy(buf + f.file->f_path.dentry->d_name.len +
+		ARRAY_SIZE(delimiter) - 1,
+		cmdline_ptr, cmdline_len - 1);
+
+	*outbuf = buf;
+	ret = size;
+
+	pr_debug("kexec cmdline buff: %s\n", buf);
+
+out:
+	if (f.file)
+		fdput(f);
+
+	return ret;
+}
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index f1d0e00a3971..d287e139085c 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -191,6 +191,8 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 	int ret = 0;
 	void *ldata;
 	loff_t size;
+	char *buff_to_measure = NULL;
+	int buff_to_measure_size = 0;
 
 	ret = kernel_read_file_from_fd(kernel_fd, &image->kernel_buf,
 				       &size, INT_MAX, READING_KEXEC_IMAGE);
@@ -241,6 +243,16 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 			ret = -EINVAL;
 			goto out;
 		}
+
+		/* IMA measures the cmdline args passed to the next kernel*/
+		buff_to_measure_size =
+			kexec_cmdline_prepend_img_name(&buff_to_measure,
+			kernel_fd, image->cmdline_buf, image->cmdline_buf_len);
+
+		ima_buffer_check(buff_to_measure, buff_to_measure_size,
+					"kexec_cmdline");
+
+
 	}
 
 	/* Call arch image load handlers */
@@ -253,7 +265,9 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 
 	image->image_loader_data = ldata;
 out:
+
 	/* In case of error, free up all allocated memory in this function */
+	kfree(buff_to_measure);
 	if (ret)
 		kimage_file_post_load_cleanup(image);
 	return ret;
-- 
2.19.1