Re: [PATCH v1] ima: audit log files opened with O_DIRECT flag

[Dmitry Kasatkin]

On 20/05/14 06:06, Mimi Zohar wrote:
> Files are measured or appraised based on the IMA policy.  When a
> file, in policy, is opened with the O_DIRECT flag, a deadlock
> occurs.
>
> The first attempt at resolving this lockdep temporarily removed the
> O_DIRECT flag and restored it, after calculating the hash.  The
> second attempt introduced the O_DIRECT_HAVELOCK flag. Based on this
> flag, do_blockdev_direct_IO() would skip taking the i_mutex a second
> time.  The third attempt, by Dmitry Kasatkin, resolves the i_mutex
> locking issue, by re-introducing the IMA mutex, but uncovered
> another problem.  Reading a file with O_DIRECT flag set, writes
> directly to userspace pages.  A second patch allocates a user-space
> like memory.  This works for all IMA hooks, except ima_file_free(),
> which is called on __fput() to recalculate the file hash.
>
> Until this last issue is addressed, do not 'collect' the
> measurement for measuring, appraising, or auditing files opened
> with the O_DIRECT flag set.  Based on policy, permit or deny file
> access.  This patch defines a new IMA policy rule option named
> 'permit_directio'.  Policy rules could be defined, based on LSM
> or other criteria, to permit specific applications to open files
> with the O_DIRECT flag set.
>
> Changelog v1:
> - permit or deny file access based IMA policy rules
>
> Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>

Acked-by: Dmitry Kasatkin <d.kasatkin@xxxxxxxxxxx>

> ---
>  Documentation/ABI/testing/ima_policy |  2 +-
>  security/integrity/ima/ima_api.c     | 10 +++++++++-
>  security/integrity/ima/ima_main.c    |  5 ++++-
>  security/integrity/ima/ima_policy.c  |  6 +++++-
>  security/integrity/integrity.h       |  1 +
>  5 files changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
> index f1c5cc9..4c3efe4 100644
> --- a/Documentation/ABI/testing/ima_policy
> +++ b/Documentation/ABI/testing/ima_policy
> @@ -23,7 +23,7 @@ Description:
>  				 [fowner]]
>  			lsm:	[[subj_user=] [subj_role=] [subj_type=]
>  				 [obj_user=] [obj_role=] [obj_type=]]
> -			option:	[[appraise_type=]]
> +			option:	[[appraise_type=]] [permit_directio]
>  
>  		base: 	func:= [BPRM_CHECK][MMAP_CHECK][FILE_CHECK][MODULE_CHECK]
>  			mask:= [MAY_READ] [MAY_WRITE] [MAY_APPEND] [MAY_EXEC]
> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
> index ba9e4d7..d719978 100644
> --- a/security/integrity/ima/ima_api.c
> +++ b/security/integrity/ima/ima_api.c
> @@ -199,6 +199,7 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
>  			    struct evm_ima_xattr_data **xattr_value,
>  			    int *xattr_len)
>  {
> +	const char *audit_cause = "failed";
>  	struct inode *inode = file_inode(file);
>  	const char *filename = file->f_dentry->d_name.name;
>  	int result = 0;
> @@ -213,6 +214,12 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
>  	if (!(iint->flags & IMA_COLLECTED)) {
>  		u64 i_version = file_inode(file)->i_version;
>  
> +		if (file->f_flags & O_DIRECT) {
> +			audit_cause = "failed(directio)";
> +			result = -EACCES;
> +			goto out;
> +		}
> +	
>  		/* use default hash algorithm */
>  		hash.hdr.algo = ima_hash_algo;
>  
> @@ -233,9 +240,10 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
>  				result = -ENOMEM;
>  		}
>  	}
> +out:
>  	if (result)
>  		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
> -				    filename, "collect_data", "failed",
> +				    filename, "collect_data", audit_cause,
>  				    result, 0);
>  	return result;
>  }
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 52ac6cf..27ab5df 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -214,8 +214,11 @@ static int process_measurement(struct file *file, const char *filename,
>  		xattr_ptr = &xattr_value;
>  
>  	rc = ima_collect_measurement(iint, file, xattr_ptr, &xattr_len);
> -	if (rc != 0)
> +	if (rc != 0) {
> +		if (file->f_flags & O_DIRECT)
> +		     rc = (iint->flags & IMA_PERMIT_DIRECTIO) ? 0 : -EACCES;
>  		goto out_digsig;
> +	}
>  
>  	pathname = filename ?: ima_d_path(&file->f_path, &pathbuf);
>  
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 93873a4..40a7488 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -353,7 +353,7 @@ enum {
>  	Opt_obj_user, Opt_obj_role, Opt_obj_type,
>  	Opt_subj_user, Opt_subj_role, Opt_subj_type,
>  	Opt_func, Opt_mask, Opt_fsmagic, Opt_uid, Opt_fowner,
> -	Opt_appraise_type, Opt_fsuuid
> +	Opt_appraise_type, Opt_fsuuid, Opt_permit_directio
>  };
>  
>  static match_table_t policy_tokens = {
> @@ -375,6 +375,7 @@ static match_table_t policy_tokens = {
>  	{Opt_uid, "uid=%s"},
>  	{Opt_fowner, "fowner=%s"},
>  	{Opt_appraise_type, "appraise_type=%s"},
> +	{Opt_permit_directio, "permit_directio"},
>  	{Opt_err, NULL}
>  };
>  
> @@ -622,6 +623,9 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
>  			else
>  				result = -EINVAL;
>  			break;
> +		case Opt_permit_directio:
> +			entry->flags |= IMA_PERMIT_DIRECTIO;
> +			break;
>  		case Opt_err:
>  			ima_log_string(ab, "UNKNOWN", p);
>  			result = -EINVAL;
> diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
> index 2fb5e53..33c0a70 100644
> --- a/security/integrity/integrity.h
> +++ b/security/integrity/integrity.h
> @@ -30,6 +30,7 @@
>  #define IMA_ACTION_FLAGS	0xff000000
>  #define IMA_DIGSIG		0x01000000
>  #define IMA_DIGSIG_REQUIRED	0x02000000
> +#define IMA_PERMIT_DIRECTIO	0x04000000
>  
>  #define IMA_DO_MASK		(IMA_MEASURE | IMA_APPRAISE | IMA_AUDIT | \
>  				 IMA_APPRAISE_SUBMASK)

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