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Subject[PATCH 1/2] unwind: prevent KASAN false positive warnings in guess unwinder
Date
The guess unwinder scans the entire stack, which can cause KASAN
"stack-out-of-bounds" false positive warnings. Tell KASAN to ignore it.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
arch/x86/kernel/unwind_guess.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/unwind_guess.c b/arch/x86/kernel/unwind_guess.c
index 2d721e5..b80e8bf 100644
--- a/arch/x86/kernel/unwind_guess.c
+++ b/arch/x86/kernel/unwind_guess.c
@@ -7,11 +7,13 @@

unsigned long unwind_get_return_address(struct unwind_state *state)
{
+ unsigned long addr = READ_ONCE_NOCHECK(*state->sp);
+
if (unwind_done(state))
return 0;

return ftrace_graph_ret_addr(state->task, &state->graph_idx,
- *state->sp, state->sp);
+ addr, state->sp);
}
EXPORT_SYMBOL_GPL(unwind_get_return_address);

@@ -23,8 +25,10 @@ bool unwind_next_frame(struct unwind_state *state)
return false;

do {
+ unsigned long addr = READ_ONCE_NOCHECK(*state->sp);
+
for (state->sp++; state->sp < info->end; state->sp++)
- if (__kernel_text_address(*state->sp))
+ if (__kernel_text_address(addr))
return true;

state->sp = info->next_sp;
--
2.7.4
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