Messages in this thread | | | Date | Wed, 26 May 2010 14:40:06 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH -mm 1/1] ptrace: PTRACE_GETFDPIC: fix the unsafe usage of child->mm |
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On 05/25, Mike Frysinger wrote: > > On Tue, May 25, 2010 at 06:23, Oleg Nesterov wrote: > > - arch/blackfin/kernel/ptrace.c:is_user_addr_valid() > > needs mmap_sem around find_vma() > > > > The lockless access to mm->context.sram_list doesn't look > > safe to me. > > > > If we add get_task_mm() - this protects us against > > destroy_context() only. What is the tracee's sub-thread > > does sys_sram_alloc() or sys_sram_free() in parallel? > > i dont believe there are any code paths in UP systems where this would > be a practical problem because sram_list is only updated by syscalls > from userspace.
Yes sure, UP && !PREEMPT is safe.
> we probably should add proper locking to this > structure though.
Agreed. I'll try to make the trivial patch tomorrow. I think we can just use mm->mmap_sem, is_user_addr_valid() needs this lock for find_vma() anyway.
Oleg.
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