From 00a5dfdb93f74e4d95fb0d83c890728e331f8810 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Fri, 5 Aug 2005 23:05:27 +0200 Subject: [PATCH] [PATCH] Fix semundo lock leakage semundo->lock can leak if semundo->refcount goes from 2 to 1 while another thread has it locked. This causes major problems for PREEMPT kernels. The simplest fix for now is to undo the single-thread optimization. This bug was found via relentless testing by Dominik Karall. Signed-off-by: Ingo Molnar Signed-off-by: Linus Torvalds --- ipc/sem.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/ipc/sem.c b/ipc/sem.c index 7e8a25c82e..70975ce078 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -895,7 +895,7 @@ static inline void lock_semundo(void) struct sem_undo_list *undo_list; undo_list = current->sysvsem.undo_list; - if ((undo_list != NULL) && (atomic_read(&undo_list->refcnt) != 1)) + if (undo_list) spin_lock(&undo_list->lock); } @@ -915,7 +915,7 @@ static inline void unlock_semundo(void) struct sem_undo_list *undo_list; undo_list = current->sysvsem.undo_list; - if ((undo_list != NULL) && (atomic_read(&undo_list->refcnt) != 1)) + if (undo_list) spin_unlock(&undo_list->lock); } @@ -943,9 +943,7 @@ static inline int get_undo_list(struct sem_undo_list **undo_listp) if (undo_list == NULL) return -ENOMEM; memset(undo_list, 0, size); - /* don't initialize unodhd->lock here. It's done - * in copy_semundo() instead. - */ + spin_lock_init(&undo_list->lock); atomic_set(&undo_list->refcnt, 1); current->sysvsem.undo_list = undo_list; } @@ -1231,8 +1229,6 @@ int copy_semundo(unsigned long clone_flags, struct task_struct *tsk) error = get_undo_list(&undo_list); if (error) return error; - if (atomic_read(&undo_list->refcnt) == 1) - spin_lock_init(&undo_list->lock); atomic_inc(&undo_list->refcnt); tsk->sysvsem.undo_list = undo_list; } else -- 2.39.5