From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4DF6D41D4F1; Sat, 12 Sep 2026 10:27:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789208864; cv=none; b=KDKfAH/A9fkFFMN9Iv0ES7ya8ADPnN8wMglEvpyEt3fEenmtoh1guNPfptqPoCH2T+AYeWJ6Wi8F7MiT+bUY8fXel2+UUWDflqe1MOx7tt/049egt/T31XT8mekkMbeNgGIFs4ugxhMQmKdiB8WJZRhU/tLrrp0guIjUZ5x7yc0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789208864; c=relaxed/simple; bh=pcwKnSh7mLDn9iyrHTGO8cfBmHrhB9AKMw4ovSADiNM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Okx5jGPojiAUOqu4QJGpWzbni3buuGOmM2cv2FwGbeT+lkdDRw+1ha/gYS6V/qtY3F01K8LzvGgb/WMPZtvW7u/FdQ2Vy8zJT3i6q5VRUxoyRcElEztYI9c5RKn8Qrmq8a+QrBXAPThb+GnIeTOiaiwMwV4pr4l+8ryyke5pg38= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=rFNv7A1d; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="rFNv7A1d" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C71731F000FF; Sat, 12 Sep 2026 10:27:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789208857; bh=+0t0pR084F2Wu5+Sme1idf3fiM8r9thPnh6E5aj3ve4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=rFNv7A1dQ8azmwgOSnp+7jRThi1KRmki94IEk3f4v9VyiXGlox+NeAdapJR7hpeSU kvQa9E5S27OFnMXYeDwSbe6iQnYM7QhSoEdhSkp6l84o7fnt0JGg4JZUg1Qz60ucq1 5ongwOEsE9R4fvr0PAtvcyT0Qh/4UsxrVXEwMvWM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sashiko , Pu Lehui , Andrii Nakryiko , Emil Tsalapatis , Amery Hung , Leon Hwang , Sasha Levin Subject: [PATCH 6.18 0704/1518] bpf: Fix potential UAF when reading bpf link info Date: Sat, 12 Sep 2026 08:47:53 +0200 Message-ID: <20260912065639.358736902@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065623.398859879@linuxfoundation.org> References: <20260912065623.398859879@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Pu Lehui [ Upstream commit 863f3ddd0b8ac65abfb50d3be0869268ac0e277b ] In bpf_link_show_fdinfo and bpf_link_get_info_by_fd, link->prog is accessed without holding any locks. If the prog is concurrently replaced via bpf_link_update, the old prog can be freed, leading to a potential UAF issue. Fix this by accessing link->prog under RCU protection to safely fetch the pointer and guarantee its lifetime while reading its fields. Fixes: 0c991ebc8c69 ("bpf: Implement bpf_prog replacement for an active bpf_cgroup_link") Reported-by: Sashiko Signed-off-by: Pu Lehui Signed-off-by: Andrii Nakryiko Reviewed-by: Emil Tsalapatis Reviewed-by: Amery Hung Acked-by: Leon Hwang Link: https://lore.kernel.org/bpf/f87b53c0-8f00-45a6-82db-8242fa9b143f@huaweicloud.com [0] Link: https://lore.kernel.org/bpf/20260728025457.2814876-1-pulehui@huaweicloud.com Signed-off-by: Sasha Levin --- kernel/bpf/syscall.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index b8937bebf5b81..bab472152d64d 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3343,9 +3343,10 @@ static const char *bpf_link_type_strs[] = { static void bpf_link_show_fdinfo(struct seq_file *m, struct file *filp) { const struct bpf_link *link = filp->private_data; - const struct bpf_prog *prog = link->prog; + const struct bpf_prog *prog; enum bpf_link_type type = link->type; char prog_tag[sizeof(prog->tag) * 2 + 1] = { }; + u32 prog_id = 0; if (type < ARRAY_SIZE(bpf_link_type_strs) && bpf_link_type_strs[type]) { if (link->type == BPF_LINK_TYPE_KPROBE_MULTI) @@ -3362,13 +3363,20 @@ static void bpf_link_show_fdinfo(struct seq_file *m, struct file *filp) } seq_printf(m, "link_id:\t%u\n", link->id); + rcu_read_lock(); + prog = READ_ONCE(link->prog); if (prog) { bin2hex(prog_tag, prog->tag, sizeof(prog->tag)); + prog_id = prog->aux->id; + } + rcu_read_unlock(); + + if (prog) { seq_printf(m, "prog_tag:\t%s\n" "prog_id:\t%u\n", prog_tag, - prog->aux->id); + prog_id); } if (link->ops->show_fdinfo) link->ops->show_fdinfo(link, m); @@ -5372,6 +5380,7 @@ static int bpf_link_get_info_by_fd(struct file *file, { struct bpf_link_info __user *uinfo = u64_to_user_ptr(attr->info.info); struct bpf_link_info info; + const struct bpf_prog *prog; u32 info_len = attr->info.info_len; int err; @@ -5386,8 +5395,12 @@ static int bpf_link_get_info_by_fd(struct file *file, info.type = link->type; info.id = link->id; - if (link->prog) - info.prog_id = link->prog->aux->id; + + rcu_read_lock(); + prog = READ_ONCE(link->prog); + if (prog) + info.prog_id = prog->aux->id; + rcu_read_unlock(); if (link->ops->fill_link_info) { err = link->ops->fill_link_info(link, &info); -- 2.53.0