From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Davidlohr Bueso , Sedat Dilek , Rik van Riel , Manfred Spraul , Andrew Morton , Linus Torvalds , Mike Galbraith Subject: [ 36/50] ipc,shm: make shmctl_nolock lockless Date: Wed, 16 Oct 2013 10:45:22 -0700 Message-Id: <20131016174402.739583132@linuxfoundation.org> In-Reply-To: <20131016174358.335646140@linuxfoundation.org> References: <20131016174358.335646140@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.11-stable review patch. If anyone has any objections, please let me know. ------------------ From: Davidlohr Bueso commit c97cb9ccab8c85428ec21eff690642ad2ce1fa8a upstream. While the INFO cmd doesn't take the ipc lock, the STAT commands do acquire it unnecessarily. We can do the permissions and security checks only holding the rcu lock. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Davidlohr Bueso Tested-by: Sedat Dilek Cc: Rik van Riel Cc: Manfred Spraul Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Cc: Mike Galbraith Signed-off-by: Greg Kroah-Hartman --- ipc/shm.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) --- a/ipc/shm.c +++ b/ipc/shm.c @@ -889,27 +889,31 @@ static int shmctl_nolock(struct ipc_name struct shmid64_ds tbuf; int result; + rcu_read_lock(); if (cmd == SHM_STAT) { - shp = shm_lock(ns, shmid); + shp = shm_obtain_object(ns, shmid); if (IS_ERR(shp)) { err = PTR_ERR(shp); - goto out; + goto out_unlock; } result = shp->shm_perm.id; } else { - shp = shm_lock_check(ns, shmid); + shp = shm_obtain_object_check(ns, shmid); if (IS_ERR(shp)) { err = PTR_ERR(shp); - goto out; + goto out_unlock; } result = 0; } + err = -EACCES; if (ipcperms(ns, &shp->shm_perm, S_IRUGO)) goto out_unlock; + err = security_shm_shmctl(shp, cmd); if (err) goto out_unlock; + memset(&tbuf, 0, sizeof(tbuf)); kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm); tbuf.shm_segsz = shp->shm_segsz; @@ -919,8 +923,9 @@ static int shmctl_nolock(struct ipc_name tbuf.shm_cpid = shp->shm_cprid; tbuf.shm_lpid = shp->shm_lprid; tbuf.shm_nattch = shp->shm_nattch; - shm_unlock(shp); - if(copy_shmid_to_user (buf, &tbuf, version)) + rcu_read_unlock(); + + if (copy_shmid_to_user(buf, &tbuf, version)) err = -EFAULT; else err = result; @@ -931,7 +936,7 @@ static int shmctl_nolock(struct ipc_name } out_unlock: - shm_unlock(shp); + rcu_read_unlock(); out: return err; }