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Subject[PATCH] x86/unwind/orc: recheck address range after stack info was updated V2
Date
get_stack_info() detects stack type only by begin address, so we must
check that address range in question is fully covered by detected stack

Otherwise following crash is possible:
-> unwind_next_frame
case ORC_TYPE_REGS:
if (!deref_stack_regs(state, sp, &state->ip, &state->sp))
-> deref_stack_regs
-> stack_access_ok <- addr is ok, but addr+len-1 is not, exit with success
*ip = READ_ONCE_NOCHECK(regs->ip); <- Here we hit stack guard fault

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

Changes since v1:
- Do not call on_stack() twice for valid range.

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

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
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