[PATCH] ipc,shm: fix shm_file deletion races

When IPC_RMID races with other shm operations there's potential for use-after-free of the shm object's associated file (shm_file). Here's the race before this patch: TASK 1 TASK 2 -- -- shm_rmid() ipc_lock_object()

[PATCH] ipc,shm: fix shm_file deletion races

When IPC_RMID races with other shm operations there's potential for use-after-free of the shm object's associated file (shm_file). Here's the race before this patch: TASK 1 TASK 2 -- -- shm_rmid() ipc_lock_object()