From: Loris Reiff loris.reiff@liblor.ch
[ Upstream commit bb8b81e396f7afbe7c50d789e2107512274d2a35 ]
A toctou issue in `__cgroup_bpf_run_filter_getsockopt` can trigger a WARN_ON_ONCE in a check of `copy_from_user`.
`*optlen` is checked to be non-negative in the individual getsockopt functions beforehand. Changing `*optlen` in a race to a negative value will result in a `copy_from_user(ctx.optval, optval, ctx.optlen)` with `ctx.optlen` being a negative integer.
Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks") Signed-off-by: Loris Reiff loris.reiff@liblor.ch Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: Stanislav Fomichev sdf@google.com Link: https://lore.kernel.org/bpf/20210122164232.61770-1-loris.reiff@liblor.ch Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/cgroup.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 96555a8a2c545..6ec8f02f463b6 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -1442,6 +1442,11 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, goto out; }
+ if (ctx.optlen < 0) { + ret = -EFAULT; + goto out; + } + if (copy_from_user(ctx.optval, optval, min(ctx.optlen, max_optlen)) != 0) { ret = -EFAULT;