From: Pu Lehui <pulehui@huawei.com> mainline inclusion from mainline-v7.3-rc1 commit 5c5997836381010fc5907b36bc17d3b19407e933 category: bugfix bugzilla: 190889 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- In bpf_netns_link_update_prog, the checks for old_prog and prog type are currently performed locklessly before acquiring netns_bpf_mutex. This creates a race condition that can lead to a UAF issue. If two threads concurrently execute BPF_LINK_UPDATE on the same netns link, the following execution path can trigger a UAF: CPU0 CPU1 bpf_netns_link_update_prog if (old_prog && old_prog != link->prog) return -EPERM; bpf_netns_link_update_prog if (old_prog && old_prog != link->prog) ... old_prog = xchg(&link->prog, new_prog); bpf_prog_put(old_prog); if (new_prog->type != link->prog->type) <-- trigger UAF Fix this by moving the old_prog and prog->type checks inside the netns_bpf_mutex critical section. Meanwhile, use guard() to simplify lock management and avoid all the goto jumping. Fixes: 7f045a49fee0 ("bpf: Add link-based BPF program attachment to network namespace") Reported-by: Sashiko <sashiko-bot@kernel.org> Signed-off-by: Pu Lehui <pulehui@huawei.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Reviewed-by: Amery Hung <ameryhung@gmail.com> Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com> Link: https://lore.kernel.org/bpf/f87b53c0-8f00-45a6-82db-8242fa9b143f@huaweicloud... [0] Link: https://lore.kernel.org/bpf/20260728023259.2813482-1-pulehui@huaweicloud.com Signed-off-by: Chen Yuxi <chenyuxi19@huawei.com> --- kernel/bpf/net_namespace.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-) diff --git a/kernel/bpf/net_namespace.c b/kernel/bpf/net_namespace.c index 868cc2c43899..a1d14bcb67c5 100644 --- a/kernel/bpf/net_namespace.c +++ b/kernel/bpf/net_namespace.c @@ -172,33 +172,28 @@ static int bpf_netns_link_update_prog(struct bpf_link *link, struct net *net; int idx, ret; + guard(mutex)(&netns_bpf_mutex); + if (old_prog && old_prog != link->prog) return -EPERM; if (new_prog->type != link->prog->type) return -EINVAL; - mutex_lock(&netns_bpf_mutex); - net = net_link->net; - if (!net || !check_net(net)) { + if (!net || !check_net(net)) /* Link auto-detached or netns dying */ - ret = -ENOLINK; - goto out_unlock; - } + return -ENOLINK; run_array = rcu_dereference_protected(net->bpf.run_array[type], lockdep_is_held(&netns_bpf_mutex)); idx = link_index(net, type, net_link); ret = bpf_prog_array_update_at(run_array, idx, new_prog); if (ret) - goto out_unlock; + return ret; old_prog = xchg(&link->prog, new_prog); bpf_prog_put(old_prog); - -out_unlock: - mutex_unlock(&netns_bpf_mutex); - return ret; + return 0; } static int bpf_netns_link_fill_info(const struct bpf_link *link, -- 2.34.1