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Subject[PATCH 1/2] ipc,shm: move BUG_ON check into shm_lock
Date
Upon every shm_lock call, we BUG_ON if an error was returned,
indicating racing either in idr or in RMID. Move this logic
into the locking.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
ipc/shm.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/ipc/shm.c b/ipc/shm.c
index 6d76707..3152dea 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -155,8 +155,14 @@ 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))
+ if (IS_ERR(ipcp)) {
+ /*
+ * We raced in the idr lookup or with RMID,
+ * either way, the ID is busted.
+ */
+ BUG_ON(1);
return (struct shmid_kernel *)ipcp;
+ }

return container_of(ipcp, struct shmid_kernel, shm_perm);
}
@@ -191,7 +197,6 @@ 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 +263,6 @@ 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 +1195,6 @@ out_fput:
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);
--
2.1.4


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