Date: Wed, 20 Jun 2012 07:43:43 GMT From: Jukka Ukkonen <jau@iki.fi> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/169260: libkvm to use O_CLOEXEC to avoid file descriptor leaks in threaded code Message-ID: <201206200743.q5K7hh55093972@red.freebsd.org> Resent-Message-ID: <201206200750.q5K7o9cd021878@freefall.freebsd.org>
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>Number: 169260 >Category: kern >Synopsis: libkvm to use O_CLOEXEC to avoid file descriptor leaks in threaded code >Confidential: no >Severity: serious >Priority: medium >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Wed Jun 20 07:50:09 UTC 2012 >Closed-Date: >Last-Modified: >Originator: Jukka Ukkonen >Release: FreeBSD 9.0-STABLE >Organization: ----- >Environment: FreeBSD sleipnir 9.0-STABLE FreeBSD 9.0-STABLE #0: Tue Jun 19 22:26:46 EEST 2012 root@sleipnir:/usr/obj/usr/src/sys/Sleipnir amd64 >Description: In libkvm files have been opened using a call sequence... xxxfd = open (...); fcntl (xxxfd, F_SETFD, FD_CLOEXEC); In threaded code this could lead to the newly opened fd leaking to a child program, if another thread happened to call exec() during the short time window between open() and fcntl(). Now that there is O_CLOEXEC available, there is an atomic alternative... xxxfd = open (..., O_CLOEXEC); >How-To-Repeat: See full description. >Fix: Apply the attached patch. Patch attached with submission follows: --- lib/libkvm/kvm.c.orig 2012-06-17 17:48:21.000000000 +0300 +++ lib/libkvm/kvm.c 2012-06-17 17:55:25.000000000 +0300 @@ -166,7 +166,7 @@ if (mf == 0) mf = _PATH_MEM; - if ((kd->pmfd = open(mf, flag, 0)) < 0) { + if ((kd->pmfd = open(mf, (flag | O_CLOEXEC), 0)) < 0) { _kvm_syserr(kd, kd->program, "%s", mf); goto failed; } @@ -179,10 +179,7 @@ _kvm_syserr(kd, kd->program, "empty file"); goto failed; } - if (fcntl(kd->pmfd, F_SETFD, FD_CLOEXEC) < 0) { - _kvm_syserr(kd, kd->program, "%s", mf); - goto failed; - } + if (S_ISCHR(st.st_mode)) { /* * If this is a character special device, then check that @@ -191,17 +188,16 @@ * case you're working with a live kernel.) */ if (strcmp(mf, _PATH_DEVNULL) == 0) { - kd->vmfd = open(_PATH_DEVNULL, O_RDONLY); + kd->vmfd = open(_PATH_DEVNULL, + (O_RDONLY | O_CLOEXEC)); return (kd); } else if (strcmp(mf, _PATH_MEM) == 0) { - if ((kd->vmfd = open(_PATH_KMEM, flag)) < 0) { - _kvm_syserr(kd, kd->program, "%s", _PATH_KMEM); - goto failed; - } - if (fcntl(kd->vmfd, F_SETFD, FD_CLOEXEC) < 0) { + if ((kd->vmfd = open(_PATH_KMEM, + (flag | O_CLOEXEC))) < 0) { _kvm_syserr(kd, kd->program, "%s", _PATH_KMEM); goto failed; } + return (kd); } } @@ -210,14 +206,11 @@ * Initialize the virtual address translation machinery, * but first setup the namelist fd. */ - if ((kd->nlfd = open(uf, O_RDONLY, 0)) < 0) { - _kvm_syserr(kd, kd->program, "%s", uf); - goto failed; - } - if (fcntl(kd->nlfd, F_SETFD, FD_CLOEXEC) < 0) { + if ((kd->nlfd = open(uf, (O_RDONLY | O_CLOEXEC), 0)) < 0) { _kvm_syserr(kd, kd->program, "%s", uf); goto failed; } + if (strncmp(mf, _PATH_FWMEM, strlen(_PATH_FWMEM)) == 0) kd->rawdump = 1; if (_kvm_initvtop(kd) < 0) >Release-Note: >Audit-Trail: >Unformatted:
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