Messages in this thread Patch in this message | | | Subject | Re: [PATCH v3] x86/sgx: Synchronize encl->srcu in sgx_encl_release(). | Date | Mon, 04 Jan 2021 14:22:05 -0600 | From | "Haitao Huang" <> |
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On Wed, 16 Dec 2020 07:49:20 -0600, Jarkko Sakkinen <jarkko@kernel.org> wrote:
> Add synchronize_srcu_expedited() to sgx_encl_release() to catch a grace > period initiated by sgx_mmu_notifier_release(). > > A trivial example of a failing sequence with tasks A and B: > > 1. A: -> sgx_release() > 2. B: -> sgx_mmu_notifier_release() > 3. B: -> list_del_rcu() > 3. A: -> sgx_encl_release() > 4. A: -> cleanup_srcu_struct() > > The loop in sgx_release() observes an empty list because B has removed > its > entry in the middle, and calls cleanup_srcu_struct() before B has a > chance > to calls synchronize_srcu(). > > Fixes: 1728ab54b4be ("x86/sgx: Add a page reclaimer") > Suggested-by: Sean Christopherson <seanjc@google.com> > Suggested-by: Haitao Huang <haitao.huang@linux.intel.com> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> > --- > v3: Fine-tuned tags, and added missing change log for v2. > v2: Switch to synchronize_srcu_expedited(). > arch/x86/kernel/cpu/sgx/encl.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/arch/x86/kernel/cpu/sgx/encl.c > b/arch/x86/kernel/cpu/sgx/encl.c > index ee50a5010277..fe7256db6e73 100644 > --- a/arch/x86/kernel/cpu/sgx/encl.c > +++ b/arch/x86/kernel/cpu/sgx/encl.c > @@ -438,6 +438,12 @@ void sgx_encl_release(struct kref *ref) > if (encl->backing) > fput(encl->backing); > + /* > + * Each sgx_mmu_notifier_release() starts a grace period. Therefore, an > + * additional sync is required here. > + */ > + synchronize_srcu_expedited(&encl->srcu); > + > cleanup_srcu_struct(&encl->srcu); > WARN_ON_ONCE(!list_empty(&encl->mm_list));
Tested-by: Haitao Huang <haitao.huang@linux.intel.com> Thanks Haitao
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