From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 84/93] bpf:bpf_seq_printf(): handle potentially unsafe format string better Date: Mon, 08 Jun 2020 21:34:37 -0700 Message-ID: <20200609043437.8_el-FkSs%akpm@linux-foundation.org> References: <20200608212922.5b7fa74ca3f4e2444441b7f9@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:58622 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726831AbgFIEei (ORCPT ); Tue, 9 Jun 2020 00:34:38 -0400 In-Reply-To: <20200608212922.5b7fa74ca3f4e2444441b7f9@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, ast@kernel.org, daniel@iogearbox.net, hch@lst.de, hpa@zytor.com, linux-mm@kvack.org, mhiramat@kernel.org, mingo@elte.hu, mm-commits@vger.kernel.org, tglx@linutronix.de, torvalds@linux-foundation.org From: Andrew Morton Subject: bpf:bpf_seq_printf(): handle potentially unsafe format string better User the proper helper for kernel or userspace addresses based on TASK_SIZE instead of the dangerous strncpy_from_unsafe function. Cc: Christoph Hellwig Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Masami Hiramatsu Cc: Thomas Gleixner Signed-off-by: Andrew Morton --- kernel/trace/bpf_trace.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/kernel/trace/bpf_trace.c~bpf-bpf_seq_printf-handle-potentially-unsafe-format-string-better +++ a/kernel/trace/bpf_trace.c @@ -588,15 +588,17 @@ BPF_CALL_5(bpf_seq_printf, struct seq_fi } if (fmt[i] == 's') { + void *unsafe_ptr; + /* try our best to copy */ if (memcpy_cnt >= MAX_SEQ_PRINTF_MAX_MEMCPY) { err = -E2BIG; goto out; } - err = strncpy_from_unsafe_strict(bufs->buf[memcpy_cnt], - (void *) (long) args[fmt_cnt], - MAX_SEQ_PRINTF_STR_LEN); + unsafe_ptr = (void *)(long)args[fmt_cnt]; + err = strncpy_from_kernel_nofault(bufs->buf[memcpy_cnt], + unsafe_ptr, MAX_SEQ_PRINTF_STR_LEN); if (err < 0) bufs->buf[memcpy_cnt][0] = '\0'; params[fmt_cnt] = (u64)(long)bufs->buf[memcpy_cnt]; _