[PATCH v2 bpf-next 1/3] net: Fix for bpf_sysctl_set_new_value

[Raman Shukhau <ramasha@meta.com>]

Call to bpf_sysctl_set_new_value doesn't change final value
of the parameter, when called from cgroup/syscall bpf handler. No error
thrown in this case, new value is simply ignored and original value, sent
to sysctl, is set. Example (see test added to this change for BPF handler
logic):

sysctl -w net.ipv4.ip_local_reserved_ports = 11111
... cgroup/syscal handler call bpf_sysctl_set_new_value	and set 22222
sysctl net.ipv4.ip_local_reserved_ports
... returns 11111

Return value check is incorrect in __cgroup_bpf_run_filter_sysctl
specifically for the case when new value is set, as bpf_prog_run_array_cg
return 0 on success.

Signed-off-by: Raman Shukhau <ramasha@meta.com>
---
 kernel/bpf/cgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 8ba73042a239..bfc36e7ca6f6 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1739,7 +1739,7 @@ int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head,
 
 	kfree(ctx.cur_val);
 
-	if (ret == 1 && ctx.new_updated) {
+	if (ret == 0 && ctx.new_updated) {
 		kfree(*buf);
 		*buf = ctx.new_val;
 		*pcount = ctx.new_len;
-- 
2.43.0