When we want to duplicate a new process, dup_task_struct() will undergo
a series of allocations. If alloc_thread_info_node() fails, we call
free_task_struct() and return.
This seems right, but it is not. free_task_struct() will not only free
the task struct from the kmem_cache, but will also call
arch_release_task_struct(). The problem is that this function is
supposed to undo whatever arch-specific work done by
arch_dup_task_struct(), that is not yet called at this point. The
particular problem I ran accross was that in x86, we will arrive at
fpu_free() without having ever allocated it.
This code is very ancient, and according to git, it is there since the
pre-git era. But forks don't fail that often, so that made it well
hidden.
Signed-off-by: Glauber Costa <glom...@parallels.com>
Reported-by: Frederic Weisbecker <fweis...@redhat.com>
---
kernel/fork.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/fork.c b/kernel/fork.c
index 152d023..b397435 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -299,7 +299,7 @@ static struct task_struct *dup_task_struct(struct
task_struct *orig)
ti = alloc_thread_info_node(tsk, node);
if (!ti) {
- free_task_struct(tsk);
+ kmem_cache_free(task_struct_cachep, tsk);
return NULL;
}
--
1.7.11.4
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