IMA: use inode->i_lock to protect read and write counters (ad16ad00) · Commits · 戴 / test

security/integrity/ima/ima.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -106,6 +106,7 @@ struct ima_iint_cache {
		unsigned char flags;
		u8 digest[IMA_DIGEST_SIZE];
		struct mutex mutex; /* protects: version, flags, digest */
		/* protected by inode->i_lock */
		unsigned int readcount; /* measured files readcount */
		unsigned int writecount;/* measured files writecount */
		struct kref refcount; /* ima_iint_cache reference count */

security/integrity/ima/ima_main.c

+23 −34

Original line number	Diff line number	Diff line
		@@ -85,42 +85,12 @@ out:
		return found;
		}

		/* ima_read_write_check - reflect possible reading/writing errors in the PCR.
		*
		* When opening a file for read, if the file is already open for write,
		* the file could change, resulting in a file measurement error.
		*
		* Opening a file for write, if the file is already open for read, results
		* in a time of measure, time of use (ToMToU) error.
		*
		* In either case invalidate the PCR.
		*/
		enum iint_pcr_error { TOMTOU, OPEN_WRITERS };
		static void ima_read_write_check(enum iint_pcr_error error,
		struct ima_iint_cache *iint,
		struct inode *inode,
		const unsigned char *filename)
		{
		switch (error) {
		case TOMTOU:
		if (iint->readcount > 0)
		ima_add_violation(inode, filename, "invalid_pcr",
		"ToMToU");
		break;
		case OPEN_WRITERS:
		if (iint->writecount > 0)
		ima_add_violation(inode, filename, "invalid_pcr",
		"open_writers");
		break;
		}
		}

		/*
		* Update the counts given an fmode_t
		*/
		static void ima_inc_counts(struct ima_iint_cache *iint, fmode_t mode)
		{
		BUG_ON(!mutex_is_locked(&iint->mutex));
		assert_spin_locked(&iint->inode->i_lock);

		if ((mode & (FMODE_READ \| FMODE_WRITE)) == FMODE_READ)
		iint->readcount++;
		@@ -146,6 +116,7 @@ void ima_counts_get(struct file *file)
		fmode_t mode = file->f_mode;
		struct ima_iint_cache *iint;
		int rc;
		bool send_tomtou = false, send_writers = false;

		if (!iint_initialized \|\| !S_ISREG(inode->i_mode))
		return;
		@@ -153,22 +124,35 @@ void ima_counts_get(struct file *file)
		if (!iint)
		return;
		mutex_lock(&iint->mutex);
		spin_lock(&inode->i_lock);

		if (!ima_initialized)
		goto out;

		rc = ima_must_measure(iint, inode, MAY_READ, FILE_CHECK);
		if (rc < 0)
		goto out;

		if (mode & FMODE_WRITE) {
		ima_read_write_check(TOMTOU, iint, inode, dentry->d_name.name);
		if (iint->readcount)
		send_tomtou = true;
		goto out;
		}
		ima_read_write_check(OPEN_WRITERS, iint, inode, dentry->d_name.name);

		if (atomic_read(&inode->i_writecount) > 0)
		send_writers = true;
		out:
		ima_inc_counts(iint, file->f_mode);
		spin_unlock(&inode->i_lock);
		mutex_unlock(&iint->mutex);

		kref_put(&iint->refcount, iint_free);

		if (send_tomtou)
		ima_add_violation(inode, dentry->d_name.name, "invalid_pcr",
		"ToMToU");
		if (send_writers)
		ima_add_violation(inode, dentry->d_name.name, "invalid_pcr",
		"open_writers");
		}

		/*
		@@ -181,6 +165,7 @@ static void ima_dec_counts(struct ima_iint_cache iint, struct inode inode,
		bool dump = false;

		BUG_ON(!mutex_is_locked(&iint->mutex));
		assert_spin_locked(&inode->i_lock);

		if ((mode & (FMODE_READ \| FMODE_WRITE)) == FMODE_READ) {
		if (unlikely(iint->readcount == 0))
		@@ -223,7 +208,11 @@ void ima_file_free(struct file *file)
		return;

		mutex_lock(&iint->mutex);
		spin_lock(&inode->i_lock);

		ima_dec_counts(iint, inode, file);

		spin_unlock(&inode->i_lock);
		mutex_unlock(&iint->mutex);
		kref_put(&iint->refcount, iint_free);
		}

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