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From: Kees Cook <keescook@chromium.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Kees Cook <keescook@chromium.org>,
	Scott Branden <scott.branden@broadcom.com>,
	Mimi Zohar <zohar@linux.ibm.com>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Takashi Iwai <tiwai@suse.de>, Jessica Yu <jeyu@kernel.org>,
	SeongJae Park <sjpark@amazon.de>, KP Singh <kpsingh@chromium.org>,
	linux-efi@vger.kernel.org, linux-security-module@vger.kernel.org,
	linux-integrity@vger.kernel.org, selinux@vger.kernel.org,
	linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v5 12/16] IMA: Add support for file reads without contents
Date: Fri,  2 Oct 2020 10:38:24 -0700
Message-ID: <20201002173828.2099543-13-keescook@chromium.org> (raw)
In-Reply-To: <20201002173828.2099543-1-keescook@chromium.org>

From: Scott Branden <scott.branden@broadcom.com>

When the kernel_read_file LSM hook is called with contents=false, IMA
can appraise the file directly, without requiring a filled buffer. When
such a buffer is available, though, IMA can continue to use it instead
of forcing a double read here.

Signed-off-by: Scott Branden <scott.branden@broadcom.com>
Link: https://lore.kernel.org/lkml/20200706232309.12010-10-scott.branden@broadcom.com/
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
 security/integrity/ima/ima_main.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 939f53d02627..82c9d62bcb11 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -613,11 +613,8 @@ void ima_post_path_mknod(struct dentry *dentry)
 int ima_read_file(struct file *file, enum kernel_read_file_id read_id,
 		  bool contents)
 {
-	/* Reject all partial reads during appraisal. */
-	if (!contents) {
-		if (ima_appraise & IMA_APPRAISE_ENFORCE)
-			return -EACCES;
-	}
+	enum ima_hooks func;
+	u32 secid;
 
 	/*
 	 * Do devices using pre-allocated memory run the risk of the
@@ -626,7 +623,20 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id,
 	 * buffers? It may be desirable to include the buffer address
 	 * in this API and walk all the dma_map_single() mappings to check.
 	 */
-	return 0;
+
+	/*
+	 * There will be a call made to ima_post_read_file() with
+	 * a filled buffer, so we don't need to perform an extra
+	 * read early here.
+	 */
+	if (contents)
+		return 0;
+
+	/* Read entire file for all partial reads. */
+	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] = {
-- 
2.25.1


  parent reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-02 17:38 [PATCH v5 00/16] Introduce partial kernel_read_file() support Kees Cook
2020-10-02 17:38 ` [PATCH v5 01/16] fs/kernel_read_file: Remove FIRMWARE_PREALLOC_BUFFER enum Kees Cook
2020-10-06 17:17   ` James Morris
2020-10-02 17:38 ` [PATCH v5 02/16] fs/kernel_read_file: Remove FIRMWARE_EFI_EMBEDDED enum Kees Cook
2020-10-02 17:38 ` [PATCH v5 03/16] fs/kernel_read_file: Split into separate include file Kees Cook
2020-10-02 17:38 ` [PATCH v5 04/16] fs/kernel_read_file: Split into separate source file Kees Cook
2020-10-06 17:18   ` James Morris
2020-10-02 17:38 ` [PATCH v5 05/16] fs/kernel_read_file: Remove redundant size argument Kees Cook
2020-10-02 17:38 ` [PATCH v5 06/16] fs/kernel_read_file: Switch buffer size arg to size_t Kees Cook
2020-10-02 17:38 ` [PATCH v5 07/16] fs/kernel_read_file: Add file_size output argument Kees Cook
2020-10-02 17:38 ` [PATCH v5 08/16] LSM: Introduce kernel_post_load_data() hook Kees Cook
2020-10-02 17:38 ` [PATCH v5 09/16] firmware_loader: Use security_post_load_data() Kees Cook
2020-10-02 17:38 ` [PATCH v5 10/16] module: Call security_kernel_post_load_data() Kees Cook
2020-10-06 17:19   ` James Morris
2020-10-02 17:38 ` [PATCH v5 11/16] LSM: Add "contents" flag to kernel_read_file hook Kees Cook
2020-10-06 17:19   ` James Morris
2020-10-02 17:38 ` Kees Cook [this message]
2020-10-02 17:38 ` [PATCH v5 13/16] fs/kernel_file_read: Add "offset" arg for partial reads Kees Cook
2020-10-02 17:38 ` [PATCH v5 14/16] firmware: Store opt_flags in fw_priv Kees Cook
2020-10-02 17:38 ` [PATCH v5 15/16] firmware: Add request_partial_firmware_into_buf() Kees Cook
2020-10-02 17:38 ` [PATCH v5 16/16] test_firmware: Test partial read support Kees Cook

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