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bpf: Allow bpf_user_ringbuf_drain() callbacks to return 1

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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 1bfe26fb08 ("bpf: Add verifier support for custom
callback return range"), which changed the default behavior of callbacks
to only support returning 0.

This patch corrects that oversight by allowing bpf_user_ringbuf_drain()
callbacks to return 0 or 1. A follow-on patch will update the
user_ringbuf selftests to also return 1 from a bpf_user_ringbuf_drain()
callback to prevent this from regressing in the future.

Fixes: 2057156738 ("bpf: Add bpf_user_ringbuf_drain() helper")
Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221012232015.1510043-2-void@manifault.com
This commit is contained in:
David Vernet 2022-10-12 18:20:14 -05:00 committed by Andrii Nakryiko
parent 0326074ff4
commit c92a7a5224
1 changed files with 1 additions and 0 deletions
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1
kernel/bpf/verifier.c
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@ -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;
}