netdev - [PATCH net-next] bpf: fix liveness propagation to parent in spilled stack slots

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Message-Id: <058693b94f456324fd1a3d5946fa486e3a09ca06.1502974643.git.daniel@iogearbox.net>
Date:   Thu, 17 Aug 2017 14:59:40 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     davem@...emloft.net
Cc:     ecree@...arflare.com, ast@...com, netdev@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH net-next] bpf: fix liveness propagation to parent in spilled stack slots

Using parent->regs[] when propagating REG_LIVE_READ for spilled regs
doesn't work since parent->regs[] denote the set of normal registers
but not spilled ones. Propagate to the correct regs.

Fixes: dc503a8ad984 ("bpf/verifier: track liveness for pruning")
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: Edward Cree <ecree@...arflare.com>
---
 kernel/bpf/verifier.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 958ba84..40f669d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3460,7 +3460,7 @@ static bool do_propagate_liveness(const struct bpf_verifier_state *state,
 		if (parent->spilled_regs[i].live & REG_LIVE_READ)
 			continue;
 		if (state->spilled_regs[i].live == REG_LIVE_READ) {
-			parent->regs[i].live |= REG_LIVE_READ;
+			parent->spilled_regs[i].live |= REG_LIVE_READ;
 			touched = true;
 		}
 	}
-- 
1.9.3