From owner-freebsd-bugs@freebsd.org Fri Mar 11 19:20:05 2016 Return-Path: Delivered-To: freebsd-bugs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id BA744ACD632 for ; Fri, 11 Mar 2016 19:20:05 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 91C99D98 for ; Fri, 11 Mar 2016 19:20:05 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from bugs.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id u2BJK5QK056618 for ; Fri, 11 Mar 2016 19:20:05 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 207911] kiconv reference count integer overflow Date: Fri, 11 Mar 2016 19:20:05 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 11.0-CURRENT X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: cturt@hardenedbsd.org X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: freebsd-bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status bug_severity priority component assigned_to reporter Message-ID: 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: 2.1.21 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 11 Mar 2016 19:20:05 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D207911 Bug ID: 207911 Summary: kiconv reference count integer overflow Product: Base System Version: 11.0-CURRENT Hardware: Any OS: Any Status: New Severity: Affects Only Me Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: cturt@hardenedbsd.org The `kiconv` module doesn't perform checks on the reference count of its converter class before incrementing and decrementing it, sys/libkern/iconv.= c: static int iconv_register_converter(struct iconv_converter_class *dcp) { kobj_class_compile((struct kobj_class*)dcp); dcp->refs++; TAILQ_INSERT_TAIL(&iconv_converters, dcp, cc_link); return 0; } static int iconv_unregister_converter(struct iconv_converter_class *dcp) { dcp->refs--; if (dcp->refs > 1) { ICDEBUG("converter has %d references left\n", dcp->refs); return EBUSY; } TAILQ_REMOVE(&iconv_converters, dcp, cc_link); kobj_class_free((struct kobj_class*)dcp); return 0; } Since `refs` field is declared as `u_int`, if `iconv_register_converter` is called enough times it will overflow from `UINT_MAX` to `0` and then be incremented to `1`. Then when `iconv_unregister_converter` is called, the c= heck against `dcp->refs` will be bypassed and its converter class will then be f= reed even though it still has references; leading to use after free behaviour. This is mostly theoretical since it is unlikely to be possible to register = this many converter classes without encountering other issues, such as running o= ut of memory. In addition, the `iconv_register_converter` is only called on the `MOD_LOAD` event, which is root only, so is unlikely to present a security risk. --=20 You are receiving this mail because: You are the assignee for the bug.=