From owner-freebsd-bugs@freebsd.org Wed Sep 11 14:31:45 2019 Return-Path: Delivered-To: freebsd-bugs@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 2C26CD5F3F for ; Wed, 11 Sep 2019 14:31:45 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mailman.nyi.freebsd.org (mailman.nyi.freebsd.org [IPv6:2610:1c1:1:606c::50:13]) by mx1.freebsd.org (Postfix) with ESMTP id 46T48x0Pj7z41S2 for ; Wed, 11 Sep 2019 14:31:45 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: by mailman.nyi.freebsd.org (Postfix) id 0BE20D5F3D; Wed, 11 Sep 2019 14:31:45 +0000 (UTC) Delivered-To: bugs@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 0B9E4D5F3C for ; Wed, 11 Sep 2019 14:31:45 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 46T48w6YdSz41S0 for ; Wed, 11 Sep 2019 14:31:44 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2610:1c1:1:606c::50:1d]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id C5B2E7D14 for ; Wed, 11 Sep 2019 14:31:44 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org ([127.0.1.5]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id x8BEViDu007292 for ; Wed, 11 Sep 2019 14:31:44 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id x8BEViQg007291 for bugs@FreeBSD.org; Wed, 11 Sep 2019 14:31:44 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 240509] segfault in basename(3) Date: Wed, 11 Sep 2019 14:31:44 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: bin X-Bugzilla-Version: 12.0-RELEASE X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: mjg@FreeBSD.org X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: cc Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 11 Sep 2019 14:31:45 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D240509 Mateusz Guzik changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |mjg@FreeBSD.org --- Comment #1 from Mateusz Guzik --- basename is allowed to modify the passes buffer. This is documented on both FreeBSD and Linux. In the attached example the string is immutable, an atte= mpt to modify it is undefined behavior and a crash (as observed) the likely outcome. The FreeBSD implementation happens to always at least add a NUL-byte which triggers the crash here, while Linux one does not modify the string if ther= e is nothing to do. The program will trivially crash if the string is modified to get basename = to operate, e.g. by adding trailing slashes: "/home/tags///". Finally, the Linux manpage explicitly shows usage with a copied buffer: The following code snippet demonstrates the use of basename() and dirname(): char *dirc, *basec, *bname, *dname; char *path =3D "/etc/passwd"; dirc =3D strdup(path); basec =3D strdup(path); dname =3D dirname(dirc); bname =3D basename(basec); printf("dirname=3D%s, basename=3D%s\n", dname, bname); That said, there is no bug in the FreeBSD version and the code does not cra= sh on Linux because of a combination of an artifact of the implementation and = the passed argument. FreeBSD variant can be modified to match but there is real benefit to it. --=20 You are receiving this mail because: You are the assignee for the bug.=