[PATCH v3] x86/unwind/orc: Recheck address range after stack info was updated

[Dmitry Monakhov <dmtrmonakhov@yandex-team.ru>]

Otherwise crash is possible in case of other bug in IBS handling code which
is passing invalid regs to the unwinder.

Original OOPS log:
BUG: stack guard page was hit at 000000000dd984a2 (stack is 00000000d1caafca..00000000613712f0)
kernel stack overflow (page fault): 0000 [#1] SMP NOPTI
CPU: 93 PID: 23787 Comm: context_switch1 Not tainted 5.4.145 #1
RIP: 0010:unwind_next_frame
Call Trace:
 <NMI>
 perf_callchain_kernel
 get_perf_callchain
 perf_callchain
 perf_prepare_sample
 perf_event_output_forward
 __perf_event_overflow
 perf_ibs_handle_irq
 perf_ibs_nmi_handler
 nmi_handle
 default_do_nmi
 do_nmi
 end_repeat_nmi

Signed-off-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru>
---

Changelog:
 v1->v2: Do not call on_stack() twice for valid range
 v2->v3: Update commit message accrording to Josh's comments

 arch/x86/kernel/unwind_orc.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 794fdef2501a..38185aedf7d1 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -339,11 +339,11 @@ static bool stack_access_ok(struct unwind_state *state, unsigned long _addr,
 	struct stack_info *info = &state->stack_info;
 	void *addr = (void *)_addr;
 
-	if (!on_stack(info, addr, len) &&
-	    (get_stack_info(addr, state->task, info, &state->stack_mask)))
-		return false;
+	if (on_stack(info, addr, len))
+		return true;
 
-	return true;
+	return !get_stack_info(addr, state->task, info, &state->stack_mask) &&
+		on_stack(info, addr, len);
 }
 
 static bool deref_stack_reg(struct unwind_state *state, unsigned long addr,
-- 
2.7.4