[PATCH bpf-next 2/2] selftest/bpf: Ensure no module loading in bpf_setsockopt(TCP_CONGESTION)

Martin KaFai Lau
2022-08-30T23:37:34Z

This patch adds a test to ensure
bpf_setsockopt(TCP_CONGESTION, "not_exist")
will not trigger the kernel module autoload.

Before the fix:
[ 40.535829] BUG: sleeping function called from invalid context at include/linux/sched/mm.h:274
...
[ 40.552134] tcp_ca_find_autoload.constprop.0+0xcb/0x200
[ 40.552689] tcp_set_congestion_control+0x99/0x7b0
[ 40.553203] do_tcp_setsockopt+0x3ed/0x2240
...
[ 40.556041] __bpf_setsockopt+0x124/0x640

Signed-off-by: Martin KaFai Lau <martin.lau@linux.dev>
---
tools/testing/selftests/bpf/progs/setget_sockopt.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/setget_sockopt.c b/tools/testing/selftests/bpf/progs/setget_sockopt.c
index 40606ef47a38..79debf3c2f44 100644
--- a/tools/testing/selftests/bpf/progs/setget_sockopt.c
+++ b/tools/testing/selftests/bpf/progs/setget_sockopt.c
@@ -32,6 +32,7 @@ struct sockopt_test {
unsigned int flip:1;
};

+static const char not_exist_cc[] = "not_exist";
static const char cubic_cc[] = "cubic";
static const char reno_cc[] = "reno";

@@ -307,6 +308,9 @@ static int bpf_test_tcp_sockopt(__u32 i, struct loop_ctx *lc)
const char *new_cc;
int new_cc_len;

+ if (!bpf_setsockopt(ctx, IPPROTO_TCP, TCP_CONGESTION,
+ (void *)not_exist_cc, sizeof(not_exist_cc)))
+ return 1;
if (bpf_getsockopt(ctx, IPPROTO_TCP, TCP_CONGESTION, old_cc, sizeof(old_cc)))
return 1;
if (!bpf_strncmp(old_cc, sizeof(old_cc), cubic_cc)) {
--
2.30.2