Merge branch 'Allow bpf_user_ringbuf_drain() callbacks to return 1'

David Vernet says:

====================
The bpf_user_ringbuf_drain() helper function allows a BPF program to
specify a callback that is invoked when draining entries from a
BPF_MAP_TYPE_USER_RINGBUF ring buffer map. The API is meant to allow the
callback to return 0 if it wants to continue draining samples, and 1 if
it's done draining. Unfortunately, bpf_user_ringbuf_drain() landed shortly
after commit 1bfe26fb0827 ("bpf: Add verifier support for custom
callback return range"), which changed the default behavior of callbacks
to only support returning 0, and the corresponding necessary change to
bpf_user_ringbuf_drain() callbacks was missed.

This patch set fixes this oversight, and updates the user_ringbuf
selftests to return 1 in a callback to catch future instances of
regression.
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

2 files changed, 3 insertions, 2 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6f6d2d511c06..9ab7188d8f68 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6946,6 +6946,7 @@ static int set_user_ringbuf_callback_state(struct bpf_verifier_env *env,
 	__mark_reg_not_init(env, &callee->regs[BPF_REG_5]);
 
 	callee->in_callback_fn = true;
+	callee->callback_ret_range = tnum_range(0, 1);
 	return 0;
 }
 
diff --git a/tools/testing/selftests/bpf/progs/user_ringbuf_success.c b/tools/testing/selftests/bpf/progs/user_ringbuf_success.c
index 099c23d9aa21..b39093dd5715 100644
--- a/tools/testing/selftests/bpf/progs/user_ringbuf_success.c
+++ b/tools/testing/selftests/bpf/progs/user_ringbuf_success.c
@@ -47,14 +47,14 @@ record_sample(struct bpf_dynptr *dynptr, void *context)
 		if (status) {
 			bpf_printk("bpf_dynptr_read() failed: %d\n", status);
 			err = 1;
-			return 0;
+			return 1;
 		}
 	} else {
 		sample = bpf_dynptr_data(dynptr, 0, sizeof(*sample));
 		if (!sample) {
 			bpf_printk("Unexpectedly failed to get sample\n");
 			err = 2;
-			return 0;
+			return 1;
 		}
 		stack_sample = *sample;
 	}