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 -ENOENT -- 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 Reported-by: Kaiyan Mei Reviewed-by: Dongliang Mu Closes: https://lore.kernel.org/bpf/f0aa3678-79c9-47ae-9e8c-02a3d1df160a@hust.edu.cn/ Signed-off-by: Jiayuan Chen --- v1 -> v2: fix the commit message and simplify to ternary. v1: https://lore.kernel.org/bpf/20260408104732.259683-1-jiayuan.chen@linux.dev/ --- kernel/bpf/offload.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c index 0ad97d643bf49..0d6f5569588c3 100644 --- a/kernel/bpf/offload.c +++ b/kernel/bpf/offload.c @@ -435,9 +435,8 @@ 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)); + ns = net ? &net->ns : NULL; } else { args->info->ifindex = 0; ns = NULL; @@ -647,9 +646,8 @@ 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)); + ns = net ? &net->ns : NULL; } else { args->info->ifindex = 0; ns = NULL; -- 2.43.0