On Sat, 2020-07-18 at 11:00 -0700, Andy Lutomirski wrote: > On Sat, Jul 18, 2020 at 10:58 AM Yu-cheng Yu <[email protected]> wrote: > > Hi, > > > > My shadow stack tests start to have random shadow stack pointer corruption > > after > > v5.7 (excluding). The symptom looks like some locking issue or the kernel > > is > > confused about which CPU a task is on. In later tip/master, this can be > > triggered by creating two tasks and each does continuous > > pthread_create()/pthread_join(). If the kernel has max_cpus=1, the issue > > goes > > away. I also checked XSAVES/XRSTORS, but this does not seem to be an issue > > coming from there. > > What do you mean "shadow stack pointer corruption"? Is SSP itself > corrupt while running in the kernel? Is one of the MSRs getting > corrupted? Is the memory to which the shadow stack points getting > corrupted? Is the CPU rejecting an attempt to change SSP?
What I see is, a new thread after ret_from_fork() and iret back to ring-3, its shadow stack pointer (MSR_IA32_PL3_SSP) is corrupted.
