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From:   "Eric W. Biederman" <ebiederm@xmission.com>
To:     linux-kernel@vger.kernel.org
Cc:     Alexey Gladkov <legion@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Shuah Khan <shuah@kernel.org>,
        Christian Brauner <brauner@kernel.org>,
        Solar Designer <solar@openwall.com>,
        Ran Xiaokai <ran.xiaokai@zte.com.cn>,
        containers@lists.linux-foundation.org,
        =?UTF-8?q?Michal=20Koutn=C3=BD?= <mkoutny@suse.com>,
        linux-api@vger.kernel.org,
        "Eric W. Biederman" <ebiederm@xmission.com>, stable@vger.kernel.org
Date:   Wed, 16 Feb 2022 09:58:32 -0600
Message-Id: <20220216155832.680775-5-ebiederm@xmission.com>
In-Reply-To: <87ilteiz4a.fsf_-_@email.froward.int.ebiederm.org>
References: <87ilteiz4a.fsf_-_@email.froward.int.ebiederm.org>
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Subject: [PATCH v2 5/5] ucounts: Handle wrapping in is_ucounts_overlimit
Precedence: bulk

While examining is_ucounts_overlimit and reading the various messages
I realized that is_ucounts_overlimit fails to deal with counts that
may have wrapped.

Being wrapped should be a transitory state for counts and they should
never be wrapped for long, but it can happen so handle it.

Cc: stable@vger.kernel.org
Fixes: 21d1c5e386bc ("Reimplement RLIMIT_NPROC on top of ucounts")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 kernel/ucount.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/ucount.c b/kernel/ucount.c
index 65b597431c86..06ea04d44685 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -350,7 +350,8 @@ bool is_ucounts_overlimit(struct ucounts *ucounts, enum ucount_type type, unsign
 	if (rlimit > LONG_MAX)
 		max = LONG_MAX;
 	for (iter = ucounts; iter; iter = iter->ns->ucounts) {
-		if (get_ucounts_value(iter, type) > max)
+		long val = get_ucounts_value(iter, type);
+		if (val < 0 || val > max)
 			return true;
 		max = READ_ONCE(iter->ns->ucount_max[type]);
 	}
-- 
2.29.2