From: Stanislav Fomichev sdf@google.com
[ Upstream commit 00e74ae0863827d944e36e56a4ce1e77e50edb91 ]
Some socket options do getsockopt with optval=NULL to estimate the size of the final buffer (which is returned via optlen). This breaks BPF getsockopt assumptions about permitted optval buffer size. Let's enforce these assumptions only when non-NULL optval is provided.
Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks") Reported-by: Martin KaFai Lau martin.lau@kernel.org Signed-off-by: Stanislav Fomichev sdf@google.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/ZD7Js4fj5YyI2oLd@google.com/T/#mb68daf700f87a924... Link: https://lore.kernel.org/bpf/20230418225343.553806-2-sdf@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/cgroup.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index eb3e787a3a977..87174832aa86d 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -1586,7 +1586,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, goto out; }
- if (ctx.optlen > max_optlen || ctx.optlen < 0) { + if (optval && (ctx.optlen > max_optlen || ctx.optlen < 0)) { ret = -EFAULT; goto out; } @@ -1600,8 +1600,11 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, }
if (ctx.optlen != 0) { - if (copy_to_user(optval, ctx.optval, ctx.optlen) || - put_user(ctx.optlen, optlen)) { + if (optval && copy_to_user(optval, ctx.optval, ctx.optlen)) { + ret = -EFAULT; + goto out; + } + if (put_user(ctx.optlen, optlen)) { ret = -EFAULT; goto out; }