From c2c737a0461e61a34676bd0bd1bc1a70a1b4e396 Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Wed, 11 Sep 2013 14:26:23 -0700 Subject: [PATCH] ipc,shm: shorten critical region for shmat Similar to other system calls, acquire the kern_ipc_perm lock after doing the initial permission and security checks. [sasha.levin@oracle.com: dont leave do_shmat with rcu lock held] Signed-off-by: Davidlohr Bueso Tested-by: Sedat Dilek Cc: Rik van Riel Cc: Manfred Spraul Signed-off-by: Sasha Levin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/shm.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/ipc/shm.c b/ipc/shm.c index 115dccebc63e..28d19f4ece4b 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -19,6 +19,9 @@ * namespaces support * OpenVZ, SWsoft Inc. * Pavel Emelianov + * + * Better ipc lock (kern_ipc_perm.lock) handling + * Davidlohr Bueso , June 2013. */ #include @@ -1086,10 +1089,11 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr, * additional creator id... */ ns = current->nsproxy->ipc_ns; - shp = shm_lock_check(ns, shmid); + rcu_read_lock(); + shp = shm_obtain_object_check(ns, shmid); if (IS_ERR(shp)) { err = PTR_ERR(shp); - goto out; + goto out_unlock; } err = -EACCES; @@ -1100,11 +1104,13 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr, if (err) goto out_unlock; + ipc_lock_object(&shp->shm_perm); path = shp->shm_file->f_path; path_get(&path); shp->shm_nattch++; size = i_size_read(path.dentry->d_inode); - shm_unlock(shp); + ipc_unlock_object(&shp->shm_perm); + rcu_read_unlock(); err = -ENOMEM; sfd = kzalloc(sizeof(*sfd), GFP_KERNEL); @@ -1175,7 +1181,7 @@ out_nattch: return err; out_unlock: - shm_unlock(shp); + rcu_read_unlock(); out: return err; } -- 2.30.2