netdev - [PATCH bpf] bpf: Fix inner map state pruning regression.

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Date:   Wed, 10 Nov 2021 09:25:56 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     davem@...emloft.net
Cc:     daniel@...earbox.net, lmb@...udflare.com, andrii@...nel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org, kernel-team@...com
Subject: [PATCH bpf] bpf: Fix inner map state pruning regression.

From: Alexei Starovoitov <ast@...nel.org>

Introduction of map_uid made two lookups from outer map to be distinct.
That distinction is only necessary when inner map has an embedded timer.
Otherwise it will make the verifier state pruning to be conservative
which will cause complex programs to hit 1M insn_processed limit.
Tighten map_uid logic to apply to inner maps with timers only.

Fixes: 3e8ce29850f1 ("bpf: Prevent pointer mismatch in bpf_timer_init.")
Reported-by: Lorenz Bauer <lmb@...udflare.com>
Tested-by: Lorenz Bauer <lmb@...udflare.com>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
---
 kernel/bpf/verifier.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 890b3ec375a3..aab7482ed1c3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1151,7 +1151,8 @@ static void mark_ptr_not_null_reg(struct bpf_reg_state *reg)
 			/* transfer reg's id which is unique for every map_lookup_elem
 			 * as UID of the inner map.
 			 */
-			reg->map_uid = reg->id;
+			if (map_value_has_timer(map->inner_map_meta))
+				reg->map_uid = reg->id;
 		} else if (map->map_type == BPF_MAP_TYPE_XSKMAP) {
 			reg->type = PTR_TO_XDP_SOCK;
 		} else if (map->map_type == BPF_MAP_TYPE_SOCKMAP ||
-- 
2.30.2