Re: [PATCH 1/2] ima: limit the number of open-writers integrity violations

[Stefan Berger <stefanb@linux.ibm.com>]

On 2/19/25 11:21 AM, Mimi Zohar wrote:
> Each time a file in policy, that is already opened for write, is opened
> for read an open-writers integrity violation audit message is emitted
> and a violation record is added to the IMA measurement list, even if an
> open-writers violation has already been recorded.
> 
> Limit the number of open-writers integrity violations for an existing
> file open for write to one.  After the existing file open for write
> closes (__fput), subsequent open-writers integrity violations may occur.
> 
> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>


> ---
> Change log v1:
> - Basesd on Stefan's RFC comments, updated the patch description and code.
> 
>   security/integrity/ima/ima.h      |  1 +
>   security/integrity/ima/ima_main.c | 11 +++++++++--
>   2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index a4f284bd846c..7f21568544dd 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -182,6 +182,7 @@ struct ima_kexec_hdr {
>   #define IMA_CHANGE_ATTR		2
>   #define IMA_DIGSIG		3
>   #define IMA_MUST_MEASURE	4
> +#define IMA_LIMIT_VIOLATIONS	5
> 
>   /* IMA integrity metadata associated with an inode */
>   struct ima_iint_cache {
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 28b8b0db6f9b..cde3ae55d654 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -137,8 +137,13 @@ static void ima_rdwr_violation_check(struct file *file,
>   	} else {
>   		if (must_measure)
>   			set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
> -		if (inode_is_open_for_write(inode) && must_measure)
> -			send_writers = true;
> +
> +		/* Limit number of open_writers violations */
> +		if (inode_is_open_for_write(inode) && must_measure) {
> +			if (!test_and_set_bit(IMA_LIMIT_VIOLATIONS,
> +					      &iint->atomic_flags))
> +				send_writers = true;
> +		}
>   	}
> 
>   	if (!send_tomtou && !send_writers)
> @@ -167,6 +172,8 @@ static void ima_check_last_writer(struct ima_iint_cache *iint,
>   	if (atomic_read(&inode->i_writecount) == 1) {
>   		struct kstat stat;
> 
> +		clear_bit(IMA_LIMIT_VIOLATIONS, &iint->atomic_flags);
> +
>   		update = test_and_clear_bit(IMA_UPDATE_XATTR,
>   					    &iint->atomic_flags);
>   		if ((iint->flags & IMA_NEW_FILE) ||
> --
> 2.48.1
>