@@ -676,6 +676,8 @@ static struct {
{"user_ringbuf_callback_discard_dynptr", "cannot release unowned const bpf_dynptr"},
{"user_ringbuf_callback_submit_dynptr", "cannot release unowned const bpf_dynptr"},
{"user_ringbuf_callback_invalid_return", "At callback return the register R0 has value"},
+ {"user_ringbuf_callback_reinit_dynptr_mem", "Dynptr has to be an uninitialized dynptr"},
+ {"user_ringbuf_callback_reinit_dynptr_ringbuf", "Dynptr has to be an uninitialized dynptr"},
};
#define SUCCESS_TEST(_func) { _func, #_func }
@@ -18,6 +18,13 @@ struct {
__uint(type, BPF_MAP_TYPE_USER_RINGBUF);
} user_ringbuf SEC(".maps");
+struct {
+ __uint(type, BPF_MAP_TYPE_RINGBUF);
+ __uint(max_entries, 2);
+} ringbuf SEC(".maps");
+
+static int map_value;
+
static long
bad_access1(struct bpf_dynptr *dynptr, void *context)
{
@@ -175,3 +182,31 @@ int user_ringbuf_callback_invalid_return(void *ctx)
return 0;
}
+
+static long
+try_reinit_dynptr_mem(struct bpf_dynptr *dynptr, void *context)
+{
+ bpf_dynptr_from_mem(&map_value, 4, 0, dynptr);
+ return 0;
+}
+
+static long
+try_reinit_dynptr_ringbuf(struct bpf_dynptr *dynptr, void *context)
+{
+ bpf_ringbuf_reserve_dynptr(&ringbuf, 8, 0, dynptr);
+ return 0;
+}
+
+SEC("?raw_tp/sys_nanosleep")
+int user_ringbuf_callback_reinit_dynptr_mem(void *ctx)
+{
+ bpf_user_ringbuf_drain(&user_ringbuf, try_reinit_dynptr_mem, NULL, 0);
+ return 0;
+}
+
+SEC("?raw_tp/sys_nanosleep")
+int user_ringbuf_callback_reinit_dynptr_ringbuf(void *ctx)
+{
+ bpf_user_ringbuf_drain(&user_ringbuf, try_reinit_dynptr_ringbuf, NULL, 0);
+ return 0;
+}
The original support for bpf_user_ringbuf_drain callbacks simply short-circuited checks for the dynptr state, allowing users to pass PTR_TO_DYNPTR (now CONST_PTR_TO_DYNPTR) to helpers that initialize a dynptr. This bug would have also surfaced with other dynptr helpers in the future that changed dynptr view or modified it in some way. Include test cases for all cases, i.e. both bpf_dynptr_from_mem and bpf_ringbuf_reserve_dynptr, and ensure verifier rejects both of them. Without the fix, both of these programs load and pass verification. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> --- .../selftests/bpf/prog_tests/user_ringbuf.c | 2 ++ .../selftests/bpf/progs/user_ringbuf_fail.c | 35 +++++++++++++++++++ 2 files changed, 37 insertions(+)