[PATCH][SRU][bionic] UBUNTU: SAUCE: apparmor: fix nnp subset test for unconfined

[Tyler Hicks]

On 2019-10-03 12:14:58, John Johansen wrote:
> The subset test is not taking into account the unconfined exception
> which will cause profile transitions in the stacked confinement
> case to fail when no_new_privs is applied.
> 
> This fixes a regression introduced in the fix for
> https://bugs.launchpad.net/bugs/1839037
> 
> Fixes: d9b32413d82a ("UBUNTU: SAUCE: apparmor: fix nnp subset check failure when, stacking")
> BugLink: https://bugs.launchpad.net/bugs/1844186
> Signed-off-by: John Johansen <john.johansen at canonical.com>
> ---
>  security/apparmor/domain.c        |  4 ++--
>  security/apparmor/include/label.h |  1 +
>  security/apparmor/label.c         | 33 +++++++++++++++++++++++++++++++
>  3 files changed, 36 insertions(+), 2 deletions(-)
> 
> diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
> index 76cebad829fa..442550b13775 100644
> --- a/security/apparmor/domain.c
> +++ b/security/apparmor/domain.c
> @@ -797,7 +797,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
>  	 * aways results in a further reduction of permissions.
>  	 */
>  	if ((bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS) &&
> -	    !unconfined(label) && !aa_label_is_subset(new, label)) {
> +	    !unconfined(label) && !aa_label_is_unconfined_subset(new, label)) {
>  		error = -EPERM;
>  		info = "no new privs";
>  		goto audit;
> @@ -1136,7 +1136,7 @@ static int change_profile_perms_wrapper(const char *op, const char *name,
>  	 */
>  	if (task_no_new_privs(current) && !stack &&
>  	    !profile_unconfined(profile) &&
> -	    !aa_label_is_subset(target, &profile->label)) {
> +	    !aa_label_is_unconfined_subset(target, &profile->label)) {
>  		info = "no new privs";
>  		error = -EPERM;
>  	}

aa_change_hat() in Bionic is still affected by 1839037 which is why this
regression fix doesn't include a hunk for aa_change_hat(). Is it worth
sending a second revision for Bionic that has a patch that fixes 1839037
for aa_change_hat() and then revise this patch to fix the
aa_change_hat() fix?

Tyler

> diff --git a/security/apparmor/include/label.h b/security/apparmor/include/label.h
> index af22dcbbcb8a..95075bd908f3 100644
> --- a/security/apparmor/include/label.h
> +++ b/security/apparmor/include/label.h
> @@ -285,6 +285,7 @@ bool aa_label_init(struct aa_label *label, int size);
>  struct aa_label *aa_label_alloc(int size, struct aa_proxy *proxy, gfp_t gfp);
>  
>  bool aa_label_is_subset(struct aa_label *set, struct aa_label *sub);
> +bool aa_label_is_unconfined_subset(struct aa_label *set, struct aa_label *sub);
>  struct aa_profile *__aa_label_next_not_in_set(struct label_it *I,
>  					     struct aa_label *set,
>  					     struct aa_label *sub);
> diff --git a/security/apparmor/label.c b/security/apparmor/label.c
> index 324fe5c60f87..0d9741f6d860 100644
> --- a/security/apparmor/label.c
> +++ b/security/apparmor/label.c
> @@ -555,6 +555,39 @@ bool aa_label_is_subset(struct aa_label *set, struct aa_label *sub)
>  	return __aa_label_next_not_in_set(&i, set, sub) == NULL;
>  }
>  
> +/**
> + * aa_label_is_unconfined_subset - test if @sub is a subset of @set
> + * @set: label to test against
> + * @sub: label to test if is subset of @set
> + *
> + * This checks for subset but taking into account unconfined. IF
> + * @sub contains an unconfined profile that does not have a matching
> + * unconfined in @set then this will not cause the test to fail.
> + * Conversely we don't care about an unconfined in @set that is not in
> + * @sub
> + *
> + * Returns: true if @sub is special_subset of @set
> + *     else false
> + */
> +bool aa_label_is_unconfined_subset(struct aa_label *set, struct aa_label *sub)
> +{
> +	struct label_it i = { };
> +	struct aa_profile *p;
> +
> +	AA_BUG(!set);
> +	AA_BUG(!sub);
> +
> +	if (sub == set)
> +		return true;
> +
> +	do {
> +		p = __aa_label_next_not_in_set(&i, set, sub);
> +		if (p && !profile_unconfined(p))
> +			break;
> +	} while (p);
> +
> +	return p == NULL;
> +}
>  
>  
>  /**
> -- 
> 2.17.1
> 
> 
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