| Message ID | b05602fd545f3ddbb2c3e2bfd2ef5d18e85edd50.1466974736.git.luto@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, Jun 26, 2016 at 02:55:33PM -0700, Andy Lutomirski wrote: > If we call do_exit with a clean stack, we greatly reduce the risk of Nits: do_exit() > recursive oopses due to stack overflow in do_exit, and we allow s/ in do_exit// > do_exit to work even if we OOPS from an IST stack. The latter gives Append "()" to the function names. > us a much better chance of surviving long enough after we detect a > stack overflow to write out our logs. > > I intentionally separated this from the preceding patch that > disables do_exit-on-OOPS on IST stacks. This way, if we need to > revert this patch, we still end up in an acceptable state wrt stack > overflow handling. > > Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> > Signed-off-by: Andy Lutomirski <luto@kernel.org> > --- ... > diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c > index 352f022cfd5b..0d05f113805e 100644 > --- a/arch/x86/kernel/dumpstack.c > +++ b/arch/x86/kernel/dumpstack.c > @@ -226,6 +226,8 @@ unsigned long oops_begin(void) > EXPORT_SYMBOL_GPL(oops_begin); > NOKPROBE_SYMBOL(oops_begin); > > +extern void __noreturn rewind_stack_do_exit(int signr); You don't need the "extern" here. > + > void oops_end(unsigned long flags, struct pt_regs *regs, int signr) > { > if (regs && kexec_should_crash(current))
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 983e5d3a0d27..0b56666e6039 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -1153,3 +1153,14 @@ ENTRY(async_page_fault) jmp error_code END(async_page_fault) #endif + +ENTRY(rewind_stack_do_exit) + /* Prevent any naive code from trying to unwind to our caller. */ + xorl %ebp, %ebp + + movl PER_CPU_VAR(cpu_current_top_of_stack), %esi + leal -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%esi), %esp + + call do_exit +1: jmp 1b +END(rewind_stack_do_exit) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 9ee0da1807ed..b846875aeea6 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1423,3 +1423,14 @@ ENTRY(ignore_sysret) mov $-ENOSYS, %eax sysret END(ignore_sysret) + +ENTRY(rewind_stack_do_exit) + /* Prevent any naive code from trying to unwind to our caller. */ + xorl %ebp, %ebp + + movq PER_CPU_VAR(cpu_current_top_of_stack), %rax + leaq -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%rax), %rsp + + call do_exit +1: jmp 1b +END(rewind_stack_do_exit) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 352f022cfd5b..0d05f113805e 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -226,6 +226,8 @@ unsigned long oops_begin(void) EXPORT_SYMBOL_GPL(oops_begin); NOKPROBE_SYMBOL(oops_begin); +extern void __noreturn rewind_stack_do_exit(int signr); + void oops_end(unsigned long flags, struct pt_regs *regs, int signr) { if (regs && kexec_should_crash(current)) @@ -245,12 +247,15 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr) return; if (in_interrupt()) panic("Fatal exception in interrupt"); - if (((current_stack_pointer() ^ (current_top_of_stack() - 1)) - & ~(THREAD_SIZE - 1)) != 0) - panic("Fatal exception on special stack"); if (panic_on_oops) panic("Fatal exception"); - do_exit(signr); + + /* + * We're not going to return, but we might be on an IST stack or + * have very little stack space left. Rewind the stack and kill + * the task. + */ + rewind_stack_do_exit(signr); } NOKPROBE_SYMBOL(oops_end);