[PATCH 2/2] bpf: cgroup: Fix problematic bounds check

[Loris Reiff]

Since ctx.optlen is signed, a larger value than max_value could be
passed, as it is later on used as unsigned, which causes a WARN_ON_ONCE
in the copy_to_user.

Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
Signed-off-by: Loris Reiff <loris.re...@liblor.ch>
---
 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 6ec8f02f4..6aa9e10c6 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1464,7 +1464,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, 
int level,
                goto out;
        }
 
-       if (ctx.optlen > max_optlen) {
+       if (ctx.optlen > max_optlen || ctx.optlen < 0) {
                ret = -EFAULT;
                goto out;
        }
-- 
2.29.2