From: Jiayuan Chen <jiayuan.chen@linux.dev>
To: bpf@vger.kernel.org
Cc: Jiayuan Chen <jiayuan.chen@linux.dev>,
Yinhao Hu <dddddd@hust.edu.cn>,
Kaiyan Mei <M202472210@hust.edu.cn>,
Dongliang Mu <dzm91@hust.edu.cn>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Jiri Olsa <jolsa@kernel.org>, Jakub Kicinski <kuba@kernel.org>,
linux-kernel@vger.kernel.org
Subject: [PATCH bpf] bpf: Fix use-after-free in offloaded map/prog info fill
Date: Wed, 8 Apr 2026 18:47:31 +0800 [thread overview]
Message-ID: <20260408104732.259683-1-jiayuan.chen@linux.dev> (raw)
When querying info for an offloaded BPF map or program,
bpf_map_offload_info_fill_ns() and bpf_prog_offload_info_fill_ns()
obtain the network namespace with get_net(dev_net(offmap->netdev)).
However, the associated netdev's netns may be racing with teardown
during netns destruction. If the netns refcount has already reached 0,
get_net() performs a refcount_t increment on 0, triggering:
refcount_t: addition on 0; use-after-free.
Although rtnl_lock and bpf_devs_lock ensure the netdev pointer remains
valid, they cannot prevent the netns refcount from reaching zero.
Fix this by using maybe_get_net() instead of get_net(). maybe_get_net()
uses refcount_inc_not_zero() and returns NULL if the refcount is already
zero, which causes ns_get_path_cb() to fail and the caller to return
-ENODEV -- the correct behavior when the netns is being destroyed.
Fixes: 675fc275a3a2d ("bpf: offload: report device information for offloaded programs")
Fixes: 52775b33bb507 ("bpf: offload: report device information about offloaded maps")
Reported-by: Yinhao Hu <dddddd@hust.edu.cn>
Reported-by: Kaiyan Mei <M202472210@hust.edu.cn>
Reported-by: Dongliang Mu <dzm91@hust.edu.cn>
Closes: https://lore.kernel.org/bpf/f0aa3678-79c9-47ae-9e8c-02a3d1df160a@hust.edu.cn/
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
---
kernel/bpf/offload.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index 0ad97d643bf49..d6dc684d0e872 100644
--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -435,9 +435,12 @@ static struct ns_common *bpf_prog_offload_info_fill_ns(void *private_data)
if (aux->offload) {
args->info->ifindex = aux->offload->netdev->ifindex;
- net = dev_net(aux->offload->netdev);
- get_net(net);
- ns = &net->ns;
+ net = maybe_get_net(dev_net(aux->offload->netdev));
+ if (net) {
+ ns = &net->ns;
+ } else {
+ ns = NULL;
+ }
} else {
args->info->ifindex = 0;
ns = NULL;
@@ -647,9 +650,12 @@ static struct ns_common *bpf_map_offload_info_fill_ns(void *private_data)
if (args->offmap->netdev) {
args->info->ifindex = args->offmap->netdev->ifindex;
- net = dev_net(args->offmap->netdev);
- get_net(net);
- ns = &net->ns;
+ net = maybe_get_net(dev_net(args->offmap->netdev));
+ if (net) {
+ ns = &net->ns;
+ } else {
+ ns = NULL;
+ }
} else {
args->info->ifindex = 0;
ns = NULL;
--
2.43.0
reply other threads:[~2026-04-08 10:49 UTC|newest]
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