Messages in this thread | | | Date | Fri, 22 Oct 2021 00:13:47 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH] x86/unwind/orc: Handle kretprobes_trampoline |
| |
On Thu, 14 Oct 2021 19:16:43 +0900 Masami Hiramatsu <mhiramat@kernel.org> wrote:
> On Wed, 13 Oct 2021 21:52:36 -0700 > Kees Cook <keescook@chromium.org> wrote: > > > On Wed, Oct 13, 2021 at 06:41:01PM -0700, Josh Poimboeuf wrote: > > > On Mon, Oct 11, 2021 at 02:03:26PM -0700, Kees Cook wrote: > > > > On Thu, Sep 02, 2021 at 07:13:26PM -0700, Kees Cook wrote: > > > > > From: Marios Pomonis <pomonis@google.com> > > > > > > > > > > Fix a bug in the ORC unwinder when kretprobes has replaced a return > > > > > address with the address of `kretprobes_trampoline'. ORC mistakenly > > > > > assumes that the address in the stack is a return address and decrements > > > > > it by 1 in order to find the proper depth of the next frame. > > Hmm, with my fixes[1], the kretprobe_trampoline address in the stack will be > replaced with the correct return address. In that case, that behavior > sounds correct. > > [1] https://lore.kernel.org/all/163163030719.489837.2236069935502195491.stgit@devnote2/
Here is the code which I applied this on my series.
/* Find IP, SP and possibly regs: */ switch (orc->type) { case UNWIND_HINT_TYPE_CALL: ip_p = sp - sizeof(long);
if (!deref_stack_reg(state, ip_p, &state->ip)) goto err;
state->ip = unwind_recover_ret_addr(state, state->ip, (unsigned long *)ip_p); state->sp = sp; state->regs = NULL; state->prev_regs = NULL; state->signal = is_kretprobe_trampoline(state->ip); break;
Actually, this cause a build issue because I introduced more generic is_kretprobe_trampoline(). Anyway, after calling unwind_recover_ret_addr(), the state->ip should be fixed. This means that the is_kretprobe_trampoline(state->ip) always be false, and that is correct because state->ip is recovered with the correct return address which is call instruction + 5.
So this patch seems not needed, hmm...
Thank you,
-- Masami Hiramatsu <mhiramat@kernel.org>
| |