From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 417BA1FB4 for ; Fri, 3 Feb 2023 10:22:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9C09FC433EF; Fri, 3 Feb 2023 10:22:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1675419773; bh=+w4Mt7NQhz5wfTJKN9+gyiK/g8JApmAnN3joOItZmvw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gjFxccR2PrIfqBkVWyAvIwajXCXFoWdRYLQ3lbjxmaW7zRDQNHT6u6LZJQ2WZ/t6U OiFxQmDQTnjN8XJI5gYTXUnfaqYrnIhvdW9PeTRr6YLsrlFFHiXvV7Uv4mOj0bhzOj D14AkuOEK07qQjhZMtCW5PSJIKbL8hxUjVn+aKn8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Hao Sun , Daniel Borkmann , Stanislav Fomichev , Sasha Levin Subject: [PATCH 6.1 06/28] bpf: Skip task with pid=1 in send_signal_common() Date: Fri, 3 Feb 2023 11:12:54 +0100 Message-Id: <20230203101010.237145507@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230203101009.946745030@linuxfoundation.org> References: <20230203101009.946745030@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Hao Sun [ Upstream commit a3d81bc1eaef48e34dd0b9b48eefed9e02a06451 ] The following kernel panic can be triggered when a task with pid=1 attaches a prog that attempts to send killing signal to itself, also see [1] for more details: Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b CPU: 3 PID: 1 Comm: systemd Not tainted 6.1.0-09652-g59fe41b5255f #148 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x100/0x178 lib/dump_stack.c:106 panic+0x2c4/0x60f kernel/panic.c:275 do_exit.cold+0x63/0xe4 kernel/exit.c:789 do_group_exit+0xd4/0x2a0 kernel/exit.c:950 get_signal+0x2460/0x2600 kernel/signal.c:2858 arch_do_signal_or_restart+0x78/0x5d0 arch/x86/kernel/signal.c:306 exit_to_user_mode_loop kernel/entry/common.c:168 [inline] exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:203 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296 do_syscall_64+0x44/0xb0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x63/0xcd So skip task with pid=1 in bpf_send_signal_common() to avoid the panic. [1] https://lore.kernel.org/bpf/20221222043507.33037-1-sunhao.th@gmail.com Signed-off-by: Hao Sun Signed-off-by: Daniel Borkmann Acked-by: Stanislav Fomichev Link: https://lore.kernel.org/bpf/20230106084838.12690-1-sunhao.th@gmail.com Signed-off-by: Sasha Levin --- kernel/trace/bpf_trace.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 1ed08967fb97..eb8c117cc8b6 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -847,6 +847,9 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type) return -EPERM; if (unlikely(!nmi_uaccess_okay())) return -EPERM; + /* Task should not be pid=1 to avoid kernel panic. */ + if (unlikely(is_global_init(current))) + return -EPERM; if (irqs_disabled()) { /* Do an early check on signal validity. Otherwise, -- 2.39.0