From c5c8975b2eb4eb7604e8ce4f762987f56d2a96a2 Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Tue, 30 Jun 2015 14:58:36 -0700 Subject: [PATCH] ipc,shm: move BUG_ON check into shm_lock Upon every shm_lock call, we BUG_ON if an error was returned, indicating racing either in idr or in shm_destroy. Move this logic into the locking. [akpm@linux-foundation.org: simplify code] Signed-off-by: Davidlohr Bueso Cc: Manfred Spraul Cc: Davidlohr Bueso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/shm.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/ipc/shm.c b/ipc/shm.c index 6d767071c367..bd9c91f433c1 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -155,8 +155,11 @@ static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id) { struct kern_ipc_perm *ipcp = ipc_lock(&shm_ids(ns), id); - if (IS_ERR(ipcp)) - return (struct shmid_kernel *)ipcp; + /* + * We raced in the idr lookup or with shm_destroy(). Either way, the + * ID is busted. + */ + BUG_ON(IS_ERR(ipcp)); return container_of(ipcp, struct shmid_kernel, shm_perm); } @@ -191,7 +194,6 @@ static void shm_open(struct vm_area_struct *vma) struct shmid_kernel *shp; shp = shm_lock(sfd->ns, sfd->id); - BUG_ON(IS_ERR(shp)); shp->shm_atim = get_seconds(); shp->shm_lprid = task_tgid_vnr(current); shp->shm_nattch++; @@ -258,7 +260,6 @@ static void shm_close(struct vm_area_struct *vma) down_write(&shm_ids(ns).rwsem); /* remove from the list of attaches of the shm segment */ shp = shm_lock(ns, sfd->id); - BUG_ON(IS_ERR(shp)); shp->shm_lprid = task_tgid_vnr(current); shp->shm_dtim = get_seconds(); shp->shm_nattch--; @@ -1191,7 +1192,6 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr, out_nattch: down_write(&shm_ids(ns).rwsem); shp = shm_lock(ns, shmid); - BUG_ON(IS_ERR(shp)); shp->shm_nattch--; if (shm_may_destroy(ns, shp)) shm_destroy(ns, shp);