[PULL 16/18] ebpf: Fix stubs to set an error when they return failure

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

From: Markus Armbruster <armbru@redhat.com>

Stubs in ebpf_rss-stub.c return false for failure without setting an
Error.  This is wrong.  Callers may assume that the functions set an
error when they fail, and crash when they try to examine or report the
error.  Callers may also check the error instead of the return value,
and misinterpret the failure as success.

ebpf_rss_load() and ebpf_rss_load() are reachable via
virtio_net_load_ebpf().  Fix them to set an error.

ebpf_rss_set_all() is unreachable: it can only be called when the
context has an eBPF program loaded, which is impossible with eBPF
support compiled out.  Call abort() there to make that clear, and to
get rid of the latent bug.

Fixes: 00b69f1d867d (ebpf: add formal error reporting to all APIs)
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20251118154718.3969982-2-armbru@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 ebpf/ebpf_rss-stub.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/ebpf/ebpf_rss-stub.c b/ebpf/ebpf_rss-stub.c
index d0e7f99fb91..11729f3d8fb 100644
--- a/ebpf/ebpf_rss-stub.c
+++ b/ebpf/ebpf_rss-stub.c
@@ -25,6 +25,7 @@ bool ebpf_rss_is_loaded(struct EBPFRSSContext *ctx)
 
 bool ebpf_rss_load(struct EBPFRSSContext *ctx, Error **errp)
 {
+    error_setg(errp, "eBPF support is not compiled in");
     return false;
 }
 
@@ -32,6 +33,7 @@ bool ebpf_rss_load_fds(struct EBPFRSSContext *ctx, int program_fd,
                        int config_fd, int toeplitz_fd, int table_fd,
                        Error **errp)
 {
+    error_setg(errp, "eBPF support is not compiled in");
     return false;
 }
 
@@ -39,7 +41,7 @@ bool ebpf_rss_set_all(struct EBPFRSSContext *ctx, struct EBPFRSSConfig *config,
                       uint16_t *indirections_table, uint8_t *toeplitz_key,
                       Error **errp)
 {
-    return false;
+    abort();
 }
 
 void ebpf_rss_unload(struct EBPFRSSContext *ctx)
-- 
2.51.0