netdev - [PATCH bpf 2/3] bpf: zero out build_id for BPF_STACK_BUILD_ID

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Message-Id: <20190115225447.245788-2-sdf@google.com>
Date:   Tue, 15 Jan 2019 14:54:46 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, ast@...nel.org, daniel@...earbox.net,
        songliubraving@...com, Stanislav Fomichev <sdf@...gle.com>
Subject: [PATCH bpf 2/3] bpf: zero out build_id for BPF_STACK_BUILD_ID_IP

When returning BPF_STACK_BUILD_ID_IP from stack_map_get_build_id_offset,
make sure that build_id field is empty. Since we are using percpu
free list, there is a possibility that we might reuse some previous
bpf_stack_build_id with non-zero build_id.

Fixes: 615755a77b24 ("bpf: extend stackmap to save binary_build_id+offset instead of address")
Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
---
 kernel/bpf/stackmap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 8975d1768dcb..f4b57c68c45f 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -315,6 +315,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 		for (i = 0; i < trace_nr; i++) {
 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 			id_offs[i].ip = ips[i];
+			memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
 		}
 		return;
 	}
@@ -325,6 +326,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 			/* per entry fall back to ips */
 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 			id_offs[i].ip = ips[i];
+			memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
 			continue;
 		}
 		id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
-- 
2.20.1.97.g81188d93c3-goog