Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752729AbbBXTm7 (ORCPT ); Tue, 24 Feb 2015 14:42:59 -0500 Received: from smtp2.provo.novell.com ([137.65.250.81]:51072 "EHLO smtp2.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751866AbbBXTm6 (ORCPT ); Tue, 24 Feb 2015 14:42:58 -0500 Message-ID: <1424806966.6539.84.camel@stgolabs.net> Subject: [PATCH v3 3/3] tomoyo: reduce mmap_sem hold for mm->exe_file From: Davidlohr Bueso To: Tetsuo Handa Cc: akpm@linux-foundation.org, dave@stgolabs.net, linux-mm@kvack.org, linux-kernel@vger.kernel.org, takedakn@nttdata.co.jp, linux-security-module@vger.kernel.org, tomoyo-dev-en@lists.sourceforge.jp Date: Tue, 24 Feb 2015 11:42:46 -0800 In-Reply-To: <201502242035.GCI75431.LHQFOOJMFVSFtO@I-love.SAKURA.ne.jp> References: <1424324307.18191.5.camel@stgolabs.net> <201502192007.AFI30725.tHFFOOMVFOQSLJ@I-love.SAKURA.ne.jp> <1424370153.18191.12.camel@stgolabs.net> <201502200711.EIH87066.HSOJLFFOtFVOQM@I-love.SAKURA.ne.jp> <1424449696.2317.0.camel@stgolabs.net> <201502242035.GCI75431.LHQFOOJMFVSFtO@I-love.SAKURA.ne.jp> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.9 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1702 Lines: 57 The mm->exe_file is currently serialized with mmap_sem (shared) in order to both safely (1) read the file and (2) compute the realpath by calling tomoyo_realpath_from_path, making it an absolute overkill. 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 Signed-off-by: Davidlohr Bueso --- Changes from v2: remove cleanups and cp initialization. security/tomoyo/util.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/security/tomoyo/util.c b/security/tomoyo/util.c index 2952ba5..29f3b65 100644 --- a/security/tomoyo/util.c +++ b/security/tomoyo/util.c @@ -948,16 +948,19 @@ bool tomoyo_path_matches_pattern(const struct tomoyo_path_info *filename, */ const char *tomoyo_get_exe(void) { - struct mm_struct *mm = current->mm; - const char *cp = NULL; + struct file *exe_file; + const char *cp; + struct mm_struct *mm = current->mm; - if (!mm) - return NULL; - down_read(&mm->mmap_sem); - if (mm->exe_file) - cp = tomoyo_realpath_from_path(&mm->exe_file->f_path); - up_read(&mm->mmap_sem); - return cp; + if (!mm) + return NULL; + exe_file = get_mm_exe_file(mm); + if (!exe_file) + return NULL; + + cp = tomoyo_realpath_from_path(&exe_file->f_path); + fput(exe_file); + return cp; } /** -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/