linux-kernel - [PATCH 1/1 linux-next] sysv, ipc: fix security-layer leaking

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Message-Id: <1470083552-22966-1-git-send-email-fabf@skynet.be>
Date:	Mon,  1 Aug 2016 22:32:32 +0200
From:	Fabian Frederick <fabf@...net.be>
To:	Davidlohr Bueso <dbueso@...e.de>
Cc:	Manfred Spraul <manfred@...orfullife.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>, fabf@...net.be
Subject: [PATCH 1/1 linux-next] sysv, ipc: fix security-layer leaking

Commit 53dad6d3a8e5
("ipc: fix race with LSMs") updated ipc_rcu_putref() to receive
rcu freeing function but used generic ipc_rcu_free() instead
of msg_rcu_free() which does security cleaning.

Running LTP msgsnd06 with kmemleak gives the following:

cat /sys/kernel/debug/kmemleak

unreferenced object 0xffff88003c0a11f8 (size 8):
  comm "msgsnd06", pid 1645, jiffies 4294672526 (age 6.549s)
  hex dump (first 8 bytes):
    1b 00 00 00 01 00 00 00                          ........
  backtrace:
    [<ffffffff818e2c43>] kmemleak_alloc+0x23/0x40
    [<ffffffff81177f31>] kmem_cache_alloc_trace+0xe1/0x180
    [<ffffffff812d42af>] selinux_msg_queue_alloc_security+0x3f/0xd0
    [<ffffffff812cc6be>] security_msg_queue_alloc+0x2e/0x40
    [<ffffffff812b94ee>] newque+0x4e/0x150
    [<ffffffff812b8cb9>] ipcget+0x159/0x1b0
    [<ffffffff812b98d9>] SyS_msgget+0x39/0x40
    [<ffffffff818e7bdb>] entry_SYSCALL_64_fastpath+0x13/0x8f
    [<ffffffffffffffff>] 0xffffffffffffffff

Manfred Spraul suggested to fix sem.c as well and
Davidlohr Bueso to only use ipc_rcu_free in case of security
allocation failure in newary()

Signed-off-by: Fabian Frederick <fabf@...net.be>
---
This patch replaces "ipc/msg.c: fix memory leak in do_msgsnd()"
Semaphore update is untested.

 ipc/msg.c |  2 +-
 ipc/sem.c | 12 ++++++------
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/ipc/msg.c b/ipc/msg.c
index 59559a2..43e9631 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -681,7 +681,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
 		rcu_read_lock();
 		ipc_lock_object(&msq->q_perm);
 
-		ipc_rcu_putref(msq, ipc_rcu_free);
+		ipc_rcu_putref(msq, msg_rcu_free);
 		/* raced with RMID? */
 		if (!ipc_valid_object(&msq->q_perm)) {
 			err = -EIDRM;
diff --git a/ipc/sem.c b/ipc/sem.c
index 3987a97..5e318c5 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -463,7 +463,7 @@ static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns
 static inline void sem_lock_and_putref(struct sem_array *sma)
 {
 	sem_lock(sma, NULL, -1);
-	ipc_rcu_putref(sma, ipc_rcu_free);
+	ipc_rcu_putref(sma, sem_rcu_free);
 }
 
 static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
@@ -1407,7 +1407,7 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
 			rcu_read_unlock();
 			sem_io = ipc_alloc(sizeof(ushort)*nsems);
 			if (sem_io == NULL) {
-				ipc_rcu_putref(sma, ipc_rcu_free);
+				ipc_rcu_putref(sma, sem_rcu_free);
 				return -ENOMEM;
 			}
 
@@ -1441,20 +1441,20 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
 		if (nsems > SEMMSL_FAST) {
 			sem_io = ipc_alloc(sizeof(ushort)*nsems);
 			if (sem_io == NULL) {
-				ipc_rcu_putref(sma, ipc_rcu_free);
+				ipc_rcu_putref(sma, sem_rcu_free);
 				return -ENOMEM;
 			}
 		}
 
 		if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
-			ipc_rcu_putref(sma, ipc_rcu_free);
+			ipc_rcu_putref(sma, sem_rcu_free);
 			err = -EFAULT;
 			goto out_free;
 		}
 
 		for (i = 0; i < nsems; i++) {
 			if (sem_io[i] > SEMVMX) {
-				ipc_rcu_putref(sma, ipc_rcu_free);
+				ipc_rcu_putref(sma, sem_rcu_free);
 				err = -ERANGE;
 				goto out_free;
 			}
@@ -1746,7 +1746,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
 	/* step 2: allocate new undo structure */
 	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
 	if (!new) {
-		ipc_rcu_putref(sma, ipc_rcu_free);
+		ipc_rcu_putref(sma, sem_rcu_free);
 		return ERR_PTR(-ENOMEM);
 	}
 
-- 
2.8.1