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

Prakhar Srivastava
2019-04-29T21:48:01Z

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