linux-kernel - [PATCH AUTOSEL 3.18 26/29] audit: Fix extended comparison of GID/EGID

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Message-ID: <20180917030533.592-26-alexander.levin@microsoft.com>
Date:   Mon, 17 Sep 2018 03:05:53 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Ondrej Mosnáček <omosnace@...hat.com>,
        Paul Moore <paul@...l-moore.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL 3.18 26/29] audit: Fix extended comparison of GID/EGID

From: Ondrej Mosnáček <omosnace@...hat.com>

[ Upstream commit af85d1772e31fed34165a1b3decef340cf4080c0 ]

The audit_filter_rules() function in auditsc.c used the in_[e]group_p()
functions to check GID/EGID match, but these functions use the current
task's credentials, while the comparison should use the credentials of
the task given to audit_filter_rules() as a parameter (tsk).

Note that we can use group_search(cred->group_info, ...) as a
replacement for both in_group_p and in_egroup_p as these functions only
compare the parameter to cred->fsgid/egid and then call group_search.

In fact, the usage of in_group_p was even more incorrect: it compares to
cred->fsgid (which is usually equal to cred->egid) and not cred->gid.

GitHub issue:
https://github.com/linux-audit/audit-kernel/issues/82

Fixes: 37eebe39c973 ("audit: improve GID/EGID comparation logic")
Signed-off-by: Ondrej Mosnacek <omosnace@...hat.com>
Signed-off-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 kernel/auditsc.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 3a6e01013b34..889ba4c9a5e3 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -484,20 +484,20 @@ static int audit_filter_rules(struct task_struct *tsk,
 			result = audit_gid_comparator(cred->gid, f->op, f->gid);
 			if (f->op == Audit_equal) {
 				if (!result)
-					result = in_group_p(f->gid);
+					result = groups_search(cred->group_info, f->gid);
 			} else if (f->op == Audit_not_equal) {
 				if (result)
-					result = !in_group_p(f->gid);
+					result = !groups_search(cred->group_info, f->gid);
 			}
 			break;
 		case AUDIT_EGID:
 			result = audit_gid_comparator(cred->egid, f->op, f->gid);
 			if (f->op == Audit_equal) {
 				if (!result)
-					result = in_egroup_p(f->gid);
+					result = groups_search(cred->group_info, f->gid);
 			} else if (f->op == Audit_not_equal) {
 				if (result)
-					result = !in_egroup_p(f->gid);
+					result = !groups_search(cred->group_info, f->gid);
 			}
 			break;
 		case AUDIT_SGID:
-- 
2.17.1