Messages in this thread | | | Date | Fri, 23 Jul 2021 12:40:25 +0800 | From | Jisheng Zhang <> | Subject | Re: [PATCH -next v2] riscv: add VMAP_STACK overflow detection |
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On Fri, 23 Jul 2021 12:29:25 +0800 Jisheng Zhang <jszhang3@mail.ustc.edu.cn> wrote:
> On Fri, 23 Jul 2021 09:36:47 +0800 > tongtiangen <tongtiangen@huawei.com> wrote: > > > On 2021/7/23 7:54, Jisheng Zhang wrote: > > > On Thu, 22 Jul 2021 17:42:52 +0200 > > > Andreas Schwab <schwab@linux-m68k.org> wrote: > > > > > >> On Jul 22 2021, Jisheng Zhang wrote: > > >> > > >>> I think we need to pin the stack before calling get_wchan(), could you please > > >>> try below patch? > > >> > > >> Thanks, this fixes the crash for me. > > >> > > >> Andreas. > > >> > > > > > > Thanks for testing. I will send out formal patch later > > > > > > Thanks > > > > > > . > > > > > > > Hi all: > > I tried to reproduced this crash in openSUSE code repo( > > https://github.com/opensuse/kernel ), but not reproduced successfully. > > > > From the patch of problem repair, the crash is due to task->stack is > > released before calling get_wchan, the task state of maybe TASK_DEAD. > > > > VMAP_STACK is used to detect kernel stack overflow, there is no > > connection between the two, it makes me a little confused. > > I believe the bug exists from the first day of riscv mainlined. > > Since THREAD_INFO_IN_TASK=y in riscv, so when task stack can be freed > before being destroyed.
typo: task stack can be freed before task is destroyed
> > When VMAP_STACK=n, task's stack is allocated from linear mapping. When > task stack is freed, the corresponding mapping still exists, and since > get_wchan() only read, no harm is observed so far. > > When VMAP_STACK=y, task's stack is allocated from vmalloc area. When > task stack is freed, the corresponding mapping may not exist, so I expect > MMU fault here, thus the kernel panic. > > In summary, the bug isn't related with VMAP_STACK, but VMAP_STACK makes > the bug observable. > > Thanks > > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv
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