Commit 9b24fef9 authored by Fabian Frederick's avatar Fabian Frederick Committed by Linus Torvalds
Browse files

sysv, ipc: fix security-layer leaking 

Commit 53dad6d3 ("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:
      kmemleak_alloc+0x23/0x40
      kmem_cache_alloc_trace+0xe1/0x180
      selinux_msg_queue_alloc_security+0x3f/0xd0
      security_msg_queue_alloc+0x2e/0x40
      newque+0x4e/0x150
      ipcget+0x159/0x1b0
      SyS_msgget+0x39/0x40
      entry_SYSCALL_64_fastpath+0x13/0x8f

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()

Fixes: 53dad6d3 ("ipc: fix race with LSMs")
Link: http://lkml.kernel.org/r/1470083552-22966-1-git-send-email-fabf@skynet.be


Signed-off-by: default avatarFabian Frederick <fabf@skynet.be>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: <stable@vger.kernel.org>	[3.12+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b5afba29

ipc/msg.c

+1 −1
Original line number Diff line number Diff line
@@ -680,7 +680,7 @@ 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;

ipc/sem.c

+6 −6
Original line number Diff line number Diff line
@@ -438,7 +438,7 @@ 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)
@@ -1381,7 +1381,7 @@ 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;

			}
@@ -1415,20 +1415,20 @@ 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;

			}
@@ -1720,7 +1720,7 @@ 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);

	}

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