lkml.org 
[lkml]   [2021]   [Jun]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] x86/sgx: Suppress WARN on inability to sanitize EPC if ksgxd is stopped
    Le Wed, Jun 23, 2021 at 04:32:19PM +0300, Jarkko Sakkinen a écrit :
    > On Wed, Jun 16, 2021 at 02:03:09PM +0800, Du Cheng wrote:
    > > Le Tue, Jun 15, 2021 at 05:44:58PM -0700, Sean Christopherson a écrit :
    > > > Don't WARN on having unsanitized EPC pages if ksgxd is stopped early,
    > > > e.g. if sgx_init() realizes there will be no downstream consumers of EPC.
    > > > If ksgxd is stopped early, EPC pages may be left on the dirty list, but
    > > > that's ok because ksgxd is only stopped if SGX initialization failed or
    > > > if the kernel is going down. In either case, the EPC won't be used.
    > > >
    > > > This bug was exposed by the addition of KVM support, but has existed and
    > > > was hittable since the original sanitization code was added. Prior to
    > > > adding KVM support, if Launch Control was not fully enabled, e.g. when
    > > > running on older hardware, sgx_init() bailed immediately before spawning
    > > > ksgxd because X86_FEATURE_SGX was cleared if X86_FEATURE_SGX_LC was
    > > > unsupported.
    > > >
    > > > With KVM support, sgx_drv_init() handles the X86_FEATURE_SGX_LC check
    > > > manually, so now there's any easy-to-hit case where sgx_init() will spawn
    > > > ksgxd and _then_ fail to initialize, which results in sgx_init() stopping
    > > > ksgxd before it finishes sanitizing the EPC.
    > > >
    > > > Prior to KVM support, the bug was much harder to hit because it basically
    > > > required char device registration to fail.
    > > >
    > > > Reported-by: Du Cheng <ducheng2@gmail.com>
    > > > Fixes: e7e0545299d8 ("x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections")
    > > > Signed-off-by: Sean Christopherson <seanjc@google.com>
    > > > ---
    > > >
    > > > Lightly tested due to lack of hardware. I hacked the flow to verify that
    > > > stopping early will leave work pending, and that rechecking should_stop()
    > > > suppress the resulting WARN.
    > > >
    > > > arch/x86/kernel/cpu/sgx/main.c | 2 +-
    > > > 1 file changed, 1 insertion(+), 1 deletion(-)
    > > >
    > > > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
    > > > index ad904747419e..fbad2b9625a5 100644
    > > > --- a/arch/x86/kernel/cpu/sgx/main.c
    > > > +++ b/arch/x86/kernel/cpu/sgx/main.c
    > > > @@ -425,7 +425,7 @@ static int ksgxd(void *p)
    > > > __sgx_sanitize_pages(&sgx_dirty_page_list);
    > > >
    > > > /* sanity check: */
    > > > - WARN_ON(!list_empty(&sgx_dirty_page_list));
    > > > + WARN_ON(!list_empty(&sgx_dirty_page_list) && !kthread_should_stop());
    > > >
    > > > while (!kthread_should_stop()) {
    > > > if (try_to_freeze())
    > > > --
    > > > 2.32.0.272.g935e593368-goog
    > > >
    > >
    > > I applied this patch on 5.13-rc6, and it no longer causes to trigger WARN_ON()
    > > on my NUC:
    > >
    > > ```
    > >
    > > [ 0.669411] PCI-DMA: Using software bounce buffering for IO (SWIOTLB)
    > > [ 0.669412] software IO TLB: mapped [mem 0x0000000017cb9000-0x000000001bcb9000] (64MB)
    > > [ 0.672788] platform rtc_cmos: registered platform RTC device (no PNP device found)
    > > [ 0.672805] sgx: EPC section 0x30200000-0x35f7ffff
    > > [ 0.674239] Initialise system trusted keyrings
    > > [ 0.674254] Key type blacklist registered
    > >
    > > ```
    > >
    > > Regards,
    > > Du Cheng
    >
    > Can you thus give a tested-by for this?
    >
    > /Jarkko

    Certainly.

    Tested-by: Du Cheng <ducheng2@gmail.com>

    \
     
     \ /
      Last update: 2021-06-25 02:48    [W:3.777 / U:0.020 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site