linux-kernel - [RFC PATCH v1 1/4] Increase size of ucounts to atomic_long

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Message-Id: <f3c95ffedbab07f05e0e6e4e5a8bdd6c358194e7.1604335819.git.gladkov.alexey@gmail.com>
Date:   Mon,  2 Nov 2020 17:50:30 +0100
From:   Alexey Gladkov <gladkov.alexey@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>
Cc:     Alexey Gladkov <legion@...nel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Christian Brauner <christian@...uner.io>
Subject: [RFC PATCH v1 1/4] Increase size of ucounts to atomic_long_t

In order to be able to use ucounts for rlimits, the size must be increased.
For example user_struct.mq_bytes (RLIMIT_MSGQUEUE) is unsigned long.

Signed-off-by: Alexey Gladkov <gladkov.alexey@...il.com>
---
 include/linux/user_namespace.h |  4 ++--
 kernel/ucount.c                | 14 +++++++-------
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 6ef1c7109fc4..fc75af812d73 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -86,7 +86,7 @@ struct user_namespace {
 	struct ctl_table_header *sysctls;
 #endif
 	struct ucounts		*ucounts;
-	int ucount_max[UCOUNT_COUNTS];
+	long ucount_max[UCOUNT_COUNTS];
 } __randomize_layout;
 
 struct ucounts {
@@ -94,7 +94,7 @@ struct ucounts {
 	struct user_namespace *ns;
 	kuid_t uid;
 	int count;
-	atomic_t ucount[UCOUNT_COUNTS];
+	atomic_long_t ucount[UCOUNT_COUNTS];
 };
 
 extern struct user_namespace init_user_ns;
diff --git a/kernel/ucount.c b/kernel/ucount.c
index 11b1596e2542..7b2bca8582ef 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -175,14 +175,14 @@ static void put_ucounts(struct ucounts *ucounts)
 	kfree(ucounts);
 }
 
-static inline bool atomic_inc_below(atomic_t *v, int u)
+static inline bool atomic_long_inc_below(atomic_long_t *v, int u)
 {
-	int c, old;
-	c = atomic_read(v);
+	long c, old;
+	c = atomic_long_read(v);
 	for (;;) {
 		if (unlikely(c >= u))
 			return false;
-		old = atomic_cmpxchg(v, c, c+1);
+		old = atomic_long_cmpxchg(v, c, c+1);
 		if (likely(old == c))
 			return true;
 		c = old;
@@ -199,14 +199,14 @@ struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid,
 		int max;
 		tns = iter->ns;
 		max = READ_ONCE(tns->ucount_max[type]);
-		if (!atomic_inc_below(&iter->ucount[type], max))
+		if (!atomic_long_inc_below(&iter->ucount[type], max))
 			goto fail;
 	}
 	return ucounts;
 fail:
 	bad = iter;
 	for (iter = ucounts; iter != bad; iter = iter->ns->ucounts)
-		atomic_dec(&iter->ucount[type]);
+		atomic_long_dec(&iter->ucount[type]);
 
 	put_ucounts(ucounts);
 	return NULL;
@@ -216,7 +216,7 @@ void dec_ucount(struct ucounts *ucounts, enum ucount_type type)
 {
 	struct ucounts *iter;
 	for (iter = ucounts; iter; iter = iter->ns->ucounts) {
-		int dec = atomic_dec_if_positive(&iter->ucount[type]);
+		int dec = atomic_long_dec_if_positive(&iter->ucount[type]);
 		WARN_ON_ONCE(dec < 0);
 	}
 	put_ucounts(ucounts);
-- 
2.25.4