From a7e75016a0753c24d6c995bc02501ae35368e333 Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Wed, 9 Feb 2022 12:33:24 +0530
Subject: selftests/bpf: Add test for bpf_timer overwriting crash
Add a test that validates that timer value is not overwritten when doing
a copy_map_value call in the kernel. Without the prior fix, this test
triggers a crash.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220209070324.1093182-3-memxor@gmail.com
---
tools/testing/selftests/bpf/progs/timer_crash.c | 54 +++++++++++++++++++++++++
1 file changed, 54 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/timer_crash.c
(limited to 'tools/testing/selftests/bpf/progs/timer_crash.c')
diff --git a/tools/testing/selftests/bpf/progs/timer_crash.c b/tools/testing/selftests/bpf/progs/timer_crash.c
new file mode 100644
index 000000000000..f8f7944e70da
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/timer_crash.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+
+struct map_elem {
+ struct bpf_timer timer;
+ struct bpf_spin_lock lock;
+};
+
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __uint(max_entries, 1);
+ __type(key, int);
+ __type(value, struct map_elem);
+} amap SEC(".maps");
+
+struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __uint(max_entries, 1);
+ __type(key, int);
+ __type(value, struct map_elem);
+} hmap SEC(".maps");
+
+int pid = 0;
+int crash_map = 0; /* 0 for amap, 1 for hmap */
+
+SEC("fentry/do_nanosleep")
+int sys_enter(void *ctx)
+{
+ struct map_elem *e, value = {};
+ void *map = crash_map ? (void *)&hmap : (void *)&amap;
+
+ if (bpf_get_current_task_btf()->tgid != pid)
+ return 0;
+
+ *(void **)&value = (void *)0xdeadcaf3;
+
+ bpf_map_update_elem(map, &(int){0}, &value, 0);
+ /* For array map, doing bpf_map_update_elem will do a
+ * check_and_free_timer_in_array, which will trigger the crash if timer
+ * pointer was overwritten, for hmap we need to use bpf_timer_cancel.
+ */
+ if (crash_map == 1) {
+ e = bpf_map_lookup_elem(map, &(int){0});
+ if (!e)
+ return 0;
+ bpf_timer_cancel(&e->timer);
+ }
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
--
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