From owner-freebsd-bugs@freebsd.org Thu Dec 17 10:04:16 2020 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 A23454B2A2F for ; Thu, 17 Dec 2020 10:04:16 +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 4CxSJc42Xyz3DD3 for ; Thu, 17 Dec 2020 10:04:16 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: by mailman.nyi.freebsd.org (Postfix) id 8889A4B2C9B; Thu, 17 Dec 2020 10:04:16 +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 872D14B2BA3 for ; Thu, 17 Dec 2020 10:04:16 +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) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 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 4CxSJc36bZz3DFt for ; Thu, 17 Dec 2020 10:04:16 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2610:1c1:1:606c::50:1d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 59B1F1696B for ; Thu, 17 Dec 2020 10:04:16 +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 0BHA4Gjo016929 for ; Thu, 17 Dec 2020 10:04:16 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id 0BHA4GQO016928 for bugs@FreeBSD.org; Thu, 17 Dec 2020 10:04:16 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 251915] TOCTOU race between tty_signal_sessleader() and killjobc() Date: Thu, 17 Dec 2020 10:04:16 +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: CURRENT X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Some People X-Bugzilla-Who: j.piecuch96@gmail.com X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: 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: 2.1.34 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 17 Dec 2020 10:04:16 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D251915 Bug ID: 251915 Summary: TOCTOU race between tty_signal_sessleader() and killjobc() Product: Base System Version: CURRENT Hardware: Any OS: Any Status: New Severity: Affects Some People Priority: --- Component: kern Assignee: bugs@FreeBSD.org Reporter: j.piecuch96@gmail.com In tty_signal_sessleader(): if (tp->t_session !=3D NULL && tp->t_session->s_leader !=3D NULL) { p =3D tp->t_session->s_leader; PROC_LOCK(p); kern_psignal(p, sig); PROC_UNLOCK(p); } We're holding the tty lock, but not the session lock, so the s_leader may be changed to NULL right after the !=3D NULL check by a concurrent invocation = of killjobc() by the session leader. The compiler *might* optimize this and on= ly read s_leader a single time, but that's far from guaranteed. I don't have a patch because I'm not sure what the right way to deal with t= his is. We could read s_leader a single time, like this: if (tp->t_session !=3D NULL && (p =3D tp->t_session->s_leader) !=3D NULL) { PROC_LOCK(p); kern_psignal(p, sig); PROC_UNLOCK(p); } ...but the compiler may in theory still output vulnerable code. I don't know what assumptions are made in FreeBSD about what compilers can and can't do. --=20 You are receiving this mail because: You are the assignee for the bug.=