[PATCH v6 8/8] ima: add FIRMWARE_PARTIAL_READ support

[Scott Branden]

Add FIRMWARE_PARTIAL_READ support for integrity
measurement on partial reads of firmware files.

Signed-off-by: Scott Branden <scott.branden at broadcom.com>
---
 drivers/base/firmware_loader/main.c |  6 +++++-
 fs/exec.c                           |  6 ++++--
 include/linux/fs.h                  |  1 +
 security/integrity/ima/ima_main.c   | 24 +++++++++++++++++++++++-
 4 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index 93e7fee42cd4..d0c42194af17 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -483,7 +483,11 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
 	/* Already populated data member means we're loading into a buffer */
 	if (!decompress && fw_priv->data) {
 		buffer = fw_priv->data;
-		id = READING_FIRMWARE_PREALLOC_BUFFER;
+		if (fw_priv->opt == KERNEL_PREAD_PART)
+			id = READING_FIRMWARE_PARTIAL_READ;
+		else
+			id = READING_FIRMWARE_PREALLOC_BUFFER;
+
 		msize = fw_priv->allocated_size;
 	}
 
diff --git a/fs/exec.c b/fs/exec.c
index e5c241c07b75..3fbc2fee909f 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -968,7 +968,8 @@ int kernel_pread_file(struct file *file, void **buf, loff_t *size,
 		goto out;
 	}
 
-	if (id != READING_FIRMWARE_PREALLOC_BUFFER)
+	if ((id != READING_FIRMWARE_PARTIAL_READ) &&
+	    (id != READING_FIRMWARE_PREALLOC_BUFFER))
 		*buf = vmalloc(alloc_size);
 	if (!*buf) {
 		ret = -ENOMEM;
@@ -1000,7 +1001,8 @@ int kernel_pread_file(struct file *file, void **buf, loff_t *size,
 
 out_free:
 	if (ret < 0) {
-		if (id != READING_FIRMWARE_PREALLOC_BUFFER) {
+		if ((id != READING_FIRMWARE_PARTIAL_READ) &&
+		    (id != READING_FIRMWARE_PREALLOC_BUFFER)) {
 			vfree(*buf);
 			*buf = NULL;
 		}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 76d463e4a628..3affcaa7c7b2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3020,6 +3020,7 @@ extern int do_pipe_flags(int *, int);
 #define __kernel_read_file_id(id) \
 	id(UNKNOWN, unknown)		\
 	id(FIRMWARE, firmware)		\
+	id(FIRMWARE_PARTIAL_READ, firmware)	\
 	id(FIRMWARE_PREALLOC_BUFFER, firmware)	\
 	id(FIRMWARE_EFI_EMBEDDED, firmware)	\
 	id(MODULE, kernel-module)		\
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 800fb3bba418..982debd59cc4 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -609,6 +609,9 @@ void ima_post_path_mknod(struct dentry *dentry)
  */
 int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
 {
+	enum ima_hooks func;
+	u32 secid;
+
 	/*
 	 * READING_FIRMWARE_PREALLOC_BUFFER
 	 *
@@ -617,11 +620,27 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
 	 * of IMA's signature verification any more than when using two
 	 * buffers?
 	 */
-	return 0;
+	if (read_id != READING_FIRMWARE_PARTIAL_READ)
+		return 0;
+
+	if (!file) {
+		if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
+		    (ima_appraise & IMA_APPRAISE_ENFORCE)) {
+			pr_err("Prevent firmware loading_store.\n");
+			return -EACCES;	/* INTEGRITY_UNKNOWN */
+		}
+		return 0;
+	}
+
+	func = read_idmap[read_id] ?: FILE_CHECK;
+	security_task_getsecid(current, &secid);
+	return process_measurement(file, current_cred(), secid, NULL,
+				   0, MAY_READ, func);
 }
 
 const int read_idmap[READING_MAX_ID] = {
 	[READING_FIRMWARE] = FIRMWARE_CHECK,
+	[READING_FIRMWARE_PARTIAL_READ] = FIRMWARE_CHECK,
 	[READING_FIRMWARE_PREALLOC_BUFFER] = FIRMWARE_CHECK,
 	[READING_MODULE] = MODULE_CHECK,
 	[READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
@@ -648,6 +667,9 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
 	enum ima_hooks func;
 	u32 secid;
 
+	if (!file && read_id == READING_FIRMWARE_PARTIAL_READ)
+		return 0;
+
 	if (!file && read_id == READING_FIRMWARE) {
 		if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
 		    (ima_appraise & IMA_APPRAISE_ENFORCE)) {
-- 
2.17.1