[PATCH] ima: define ima_create_tmpfile() hook and add missing call

[PATCH] ima: define ima_create_tmpfile() hook and add missing call

[Mimi Zohar]

If tmpfiles can be made persistent, then newly created tmpfiles need to
be treated like any other new files in policy.

This patch indicates which newly created tmpfiles are in policy, causing
the file hash to be calculated on __fput().

Reported-by: Ignaz Forster <ignaz.forster@gmx.de>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
 fs/namei.c                        |  2 ++
 include/linux/ima.h               |  6 ++++++
 security/integrity/ima/ima_main.c | 36 ++++++++++++++++++++++++++++++++++--
 3 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 0cab6494978c..0911837979f6 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3495,6 +3495,8 @@ static int do_tmpfile(struct nameidata *nd, unsigned flags,
 		goto out2;
 	file->f_path.mnt = path.mnt;
 	error = finish_open(file, child, NULL);
+	if (!error)
+		ima_post_create_tmpfile(file);
 out2:
 	mnt_drop_write(path.mnt);
 out:
diff --git a/include/linux/ima.h b/include/linux/ima.h
index b5e16b8c50b7..2cd1577943ce 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -18,6 +18,7 @@ struct linux_binprm;
 #ifdef CONFIG_IMA
 extern int ima_bprm_check(struct linux_binprm *bprm);
 extern int ima_file_check(struct file *file, int mask);
+extern void ima_post_create_tmpfile(const struct file *file);
 extern void ima_file_free(struct file *file);
 extern int ima_file_mmap(struct file *file, unsigned long prot);
 extern int ima_load_data(enum kernel_load_data_id id);
@@ -56,6 +57,11 @@ static inline int ima_file_check(struct file *file, int mask)
 	return 0;
 }
 
+static inline void ima_post_create_tmpfile(const struct file *file)
+{
+	return 0;
+}
+
 static inline void ima_file_free(struct file *file)
 {
 	return;
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index bd9bd5f88206..388458c8ec29 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -395,6 +395,34 @@ int ima_file_check(struct file *file, int mask)
 EXPORT_SYMBOL_GPL(ima_file_check);
 
 /**
+ * ima_post_create_tmpfile - mark newly created tmpfile as new
+ * @file : newly created tmpfile
+ *
+ * No measuring, appraising or auditing of newly created tmpfiles is needed.
+ * Skip calling process_measurement(), but indicate which newly, created
+ * tmpfiles are in policy.
+ */
+void ima_post_create_tmpfile(const struct file *file)
+{
+	struct inode *inode = file_inode(file);
+	struct integrity_iint_cache *iint;
+	int must_appraise;
+
+	must_appraise = ima_must_appraise(inode, MAY_ACCESS, FILE_CHECK);
+	if (!must_appraise)
+		return;
+
+	/* Nothing to do if we can't allocate memory */
+	iint = integrity_inode_get(inode);
+	if (!iint)
+		return;
+
+	/* needed for writing the security xattrs */
+	set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
+	iint->ima_file_status = INTEGRITY_PASS;
+}
+
+/**
  * ima_post_path_mknod - mark as a new inode
  * @dentry: newly created dentry
  *
@@ -411,9 +439,13 @@ void ima_post_path_mknod(struct dentry *dentry)
 	if (!must_appraise)
 		return;
 
+	/* Nothing to do if we can't allocate memory */
 	iint = integrity_inode_get(inode);
-	if (iint)
-		iint->flags |= IMA_NEW_FILE;
+	if (!iint)
+		return;
+
+	/* needed for re-opening empty files */
+	iint->flags |= IMA_NEW_FILE;
 }
 
 /**
-- 
2.7.5

Re: [PATCH] ima: define ima_create_tmpfile() hook and add missing call

[kbuild test robot]

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Hi Mimi,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.20-rc7 next-20181217]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Mimi-Zohar/ima-define-ima_create_tmpfile-hook-and-add-missing-call/20181218-081329
config: x86_64-randconfig-x006-201850 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   In file included from fs//attr.c:19:0:
   include/linux/ima.h: In function 'ima_post_create_tmpfile':
>> include/linux/ima.h:47:9: warning: 'return' with a value, in function returning void
     return 0;
            ^
   include/linux/ima.h:45:20: note: declared here
    static inline void ima_post_create_tmpfile(const struct file *file)
                       ^~~~~~~~~~~~~~~~~~~~~~~

vim +/return +47 include/linux/ima.h

    44	
    45	static inline void ima_post_create_tmpfile(const struct file *file)
    46	{
  > 47		return 0;
    48	}
    49	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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