Messages in this thread | | | Date | Thu, 23 Aug 2012 18:38:21 +0400 | From | Glauber Costa <> | Subject | Re: [PATCH] fork: fix oops after fork failure |
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On 08/23/2012 06:33 PM, Michal Hocko wrote: > On Thu 23-08-12 17:08:46, Glauber Costa wrote: >> 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 <glommer@parallels.com> >> Reported-by: Frederic Weisbecker <fweisbec@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); > > What about ia64 (or !CONFIG_ARCH_THREAD_INFO_ALLOCATOR in general) which > doesn't allocate thread_info at all?
They would return something meaningful here anyway, otherwise this would already error out and exit.
But you actually have a point. Not all architectures (all but ia64) will allocathe the task struct from the slab... sigh...
Sorry, I will come up with something for this.
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