On 7/22/21 1:52 PM, Yu-cheng Yu wrote: > + if (!stack_size) > + stack_size = min_t(unsigned long long, rlimit(RLIMIT_STACK), SZ_4G); > + > + if (!shstk->size) > + return 0; > + > + /* > + * For CLONE_VM, except vfork, the child needs a separate shadow > + * stack. > + */ > + if ((clone_flags & (CLONE_VFORK | CLONE_VM)) != CLONE_VM) > + return 0; > + > + /* > + * This is in clone() syscall and fpu__copy() already copies xstates > + * from the parent. If get_xsave_addr() returns null, then XFEATURE_ > + * CET_USER is still in init state, which certainly is an error. > + */ > + state = get_xsave_addr(&tsk->thread.fpu.state.xsave, XFEATURE_CET_USER); > + if (!state) > + return -EINVAL; I don't care much for that comment. This code is meant to copy shadow stack config information into children when it is already enabled. We *just* checked for that above in the "shstk->size" check. The fact that this is called from clone() is irrelevant. The shadow stack enabling status *is*. I think I'd rather this be more along the lines of: /* * 'tsk' is configured with a shadow stack and the fpu.state is * up to date since it was just copied from the parent. There * must be a valid non-init CET state location in the buffer. */ There is also a strong enough assumption violation that I'd probably WARN() in addition to returning -EINVAL.
