Use of memmove() in #DF is problematic considered tracing and other instrumentation.
Remove the memmove() call and simply write out what needs doing; this even clarifies the code, win-win! The code copies from the espfix64 stack to the normal task stack, there is no possible way for that to overlap. Survives selftests/x86, specifically sigreturn_64. Suggested-by: Borislav Petkov <b...@alien8.de> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Acked-by: Andy Lutomirski <l...@kernel.org> Link: https://lkml.kernel.org/r/20200220121727.gb...@zn.tnic --- arch/x86/kernel/traps.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -278,6 +278,7 @@ dotraplinkage void do_double_fault(struc regs->ip == (unsigned long)native_irq_return_iret) { struct pt_regs *gpregs = (struct pt_regs *)this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1; + unsigned long *p = (unsigned long *)regs->sp; /* * regs->sp points to the failing IRET frame on the @@ -285,7 +286,11 @@ dotraplinkage void do_double_fault(struc * in gpregs->ss through gpregs->ip. * */ - memmove(&gpregs->ip, (void *)regs->sp, 5*8); + gpregs->ip = p[0]; + gpregs->cs = p[1]; + gpregs->flags = p[2]; + gpregs->sp = p[3]; + gpregs->ss = p[4]; gpregs->orig_ax = 0; /* Missing (lost) #GP error code */ /*
