From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f174.google.com (mail-pd0-f174.google.com [209.85.192.174]) by kanga.kvack.org (Postfix) with ESMTP id 60F536B006C for ; Sun, 22 Feb 2015 21:20:18 -0500 (EST) Received: by pdjz10 with SMTP id z10so21807140pdj.12 for ; Sun, 22 Feb 2015 18:20:18 -0800 (PST) Received: from smtp2.provo.novell.com (smtp2.provo.novell.com. [137.65.250.81]) by mx.google.com with ESMTPS id c12si4169835pdm.248.2015.02.22.18.20.16 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Sun, 22 Feb 2015 18:20:17 -0800 (PST) Message-ID: <1424658009.6539.15.camel@stgolabs.net> Subject: [PATCH v2 2/3] kernel/audit: reduce mmap_sem hold for mm->exe_file From: Davidlohr Bueso Date: Sun, 22 Feb 2015 18:20:09 -0800 In-Reply-To: <1424304641-28965-3-git-send-email-dbueso@suse.de> References: <1424304641-28965-1-git-send-email-dbueso@suse.de> <1424304641-28965-3-git-send-email-dbueso@suse.de> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, paul@paul-moore.com, eparis@redhat.com, linux-audit@redhat.com, dave@stgolabs.net The mm->exe_file is currently serialized with mmap_sem (shared) in order to both safely (1) read the file and (2) audit it via audit_log_d_path(). Good users will, on the other hand, make use of the more standard get_mm_exe_file(), requiring only holding the mmap_sem to read the value, and relying on reference counting to make sure that the exe file won't dissapear underneath us. Additionally, upon NULL return of get_mm_exe_file, we also call audit_log_format(ab, " exe=(null)"). Signed-off-by: Davidlohr Bueso --- changes from v1: rebased on top of 1/1. kernel/audit.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) diff --git a/kernel/audit.c b/kernel/audit.c index a71cbfe..b446d54 100644 --- a/kernel/audit.c +++ b/kernel/audit.c @@ -43,6 +43,7 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt +#include #include #include #include @@ -1841,15 +1842,20 @@ EXPORT_SYMBOL(audit_log_task_context); void audit_log_d_path_exe(struct audit_buffer *ab, struct mm_struct *mm) { - if (!mm) { - audit_log_format(ab, " exe=(null)"); - return; - } + struct file *exe_file; + + if (!mm) + goto out_null; - down_read(&mm->mmap_sem); - if (mm->exe_file) - audit_log_d_path(ab, " exe=", &mm->exe_file->f_path); - up_read(&mm->mmap_sem); + exe_file = get_mm_exe_file(mm); + if (!exe_file) + goto out_null; + + audit_log_d_path(ab, " exe=", &exe_file->f_path); + fput(exe_file); + return; +out_null: + audit_log_format(ab, " exe=(null)"); } void audit_log_task_info(struct audit_buffer *ab, struct task_struct *tsk) -- 2.1.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org