From: Stanislav Fomichev <sdf@google.com>
To: netdev@vger.kernel.org, bpf@vger.kernel.org
Cc: davem@davemloft.net, ast@kernel.org, daniel@iogearbox.net,
Stanislav Fomichev <sdf@google.com>
Subject: [PATCH bpf-next 1/2] bpf: always allocate at least 16 bytes for setsockopt hook
Date: Mon, 29 Jul 2019 14:51:10 -0700 [thread overview]
Message-ID: <20190729215111.209219-2-sdf@google.com> (raw)
In-Reply-To: <20190729215111.209219-1-sdf@google.com>
Since we always allocate memory, allocate just a little bit more
for the BPF program in case it need to override user input with
bigger value. The canonical example is TCP_CONGESTION where
input string might be too small to override (nv -> bbr or cubic).
16 bytes are chosen to match the size of TCP_CA_NAME_MAX and can
be extended in the future if needed.
Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
kernel/bpf/cgroup.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 0a00eaca6fae..6a6a154cfa7b 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -964,7 +964,6 @@ static int sockopt_alloc_buf(struct bpf_sockopt_kern *ctx, int max_optlen)
return -ENOMEM;
ctx->optval_end = ctx->optval + max_optlen;
- ctx->optlen = max_optlen;
return 0;
}
@@ -984,7 +983,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level,
.level = *level,
.optname = *optname,
};
- int ret;
+ int ret, max_optlen;
/* Opportunistic check to see whether we have any BPF program
* attached to the hook so we don't waste time allocating
@@ -994,10 +993,18 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level,
__cgroup_bpf_prog_array_is_empty(cgrp, BPF_CGROUP_SETSOCKOPT))
return 0;
- ret = sockopt_alloc_buf(&ctx, *optlen);
+ /* Allocate a bit more than the initial user buffer for
+ * BPF program. The canonical use case is overriding
+ * TCP_CONGESTION(nv) to TCP_CONGESTION(cubic).
+ */
+ max_optlen = max_t(int, 16, *optlen);
+
+ ret = sockopt_alloc_buf(&ctx, max_optlen);
if (ret)
return ret;
+ ctx.optlen = *optlen;
+
if (copy_from_user(ctx.optval, optval, *optlen) != 0) {
ret = -EFAULT;
goto out;
@@ -1016,7 +1023,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level,
if (ctx.optlen == -1) {
/* optlen set to -1, bypass kernel */
ret = 1;
- } else if (ctx.optlen > *optlen || ctx.optlen < -1) {
+ } else if (ctx.optlen > max_optlen || ctx.optlen < -1) {
/* optlen is out of bounds */
ret = -EFAULT;
} else {
@@ -1063,6 +1070,8 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
if (ret)
return ret;
+ ctx.optlen = max_optlen;
+
if (!retval) {
/* If kernel getsockopt finished successfully,
* copy whatever was returned to the user back
--
2.22.0.709.g102302147b-goog
next prev parent reply other threads:[~2019-07-29 21:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-29 21:51 [PATCH bpf-next 0/2] bpf: allocate extra memory for setsockopt hook buffer Stanislav Fomichev
2019-07-29 21:51 ` Stanislav Fomichev [this message]
2019-07-29 21:51 ` [PATCH bpf-next 2/2] selftests/bpf: extend sockopt_sk selftest with TCP_CONGESTION use case Stanislav Fomichev
2019-08-01 20:58 ` [PATCH bpf-next 0/2] bpf: allocate extra memory for setsockopt hook buffer Alexei Starovoitov
2019-08-01 21:11 ` Stanislav Fomichev
2019-08-01 21:29 ` Alexei Starovoitov
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