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authorIngo Molnar <mingo@elte.hu>2005-08-05 23:05:27 +0200
committerLinus Torvalds <torvalds@g5.osdl.org>2005-08-05 15:56:41 -0700
commit00a5dfdb93f74e4d95fb0d83c890728e331f8810 (patch)
treef1d1043d7d02ad6bde3b158807b28bcfdafa21f6 /ipc/sem.c
parent[PATCH] blk: fix tag shrinking (revive real_max_size) (diff)
downloadlinux-dev-00a5dfdb93f74e4d95fb0d83c890728e331f8810.tar.xz
linux-dev-00a5dfdb93f74e4d95fb0d83c890728e331f8810.zip
[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 <mingo@elte.hu> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'ipc/sem.c')
-rw-r--r--ipc/sem.c10
1 files changed, 3 insertions, 7 deletions
diff --git a/ipc/sem.c b/ipc/sem.c
index 7e8a25c82ef3..70975ce0784a 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