Date: Thu, 5 Mar 2015 21:45:52 +0100 From: Mateusz Guzik <mjguzik@gmail.com> To: Chagin Dmitry <dchagin@freebsd.org> Cc: src-committers@freebsd.org, svn-src-user@freebsd.org Subject: Re: svn commit: r279335 - in user/dchagin/lemul/sys: compat/linprocfs fs/procfs fs/pseudofs modules/procfs Message-ID: <20150305204552.GC11164@dft-labs.eu> In-Reply-To: <20150227195329.GA7995@dchagin.static.corbina.net> References: <201502262130.t1QLUfwf027872@svn.freebsd.org> <20150226220342.GC3799@dft-labs.eu> <20150227195329.GA7995@dchagin.static.corbina.net>
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On Fri, Feb 27, 2015 at 10:53:29PM +0300, Chagin Dmitry wrote: > On Thu, Feb 26, 2015 at 11:03:42PM +0100, Mateusz Guzik wrote: > > On Thu, Feb 26, 2015 at 09:30:41PM +0000, Dmitry Chagin wrote: > > > +int > > > +procfs_dofdlink(PFS_FILL_ARGS) > > > +{ > > > + char *fullpath, *freepath, *endfileno; > > > + struct filedesc *fdp; > > > + struct vnode *vp; > > > + struct file *fp; > > > + int fileno, error; > > > + > > > + if (vnode_name == NULL) > > > + return (ENOENT); > > > + > > > + fileno = (int)strtol(vnode_name, &endfileno, 10); > > > + if (fileno == 0 && (vnode_namelen > 1 || > > > + (vnode_namelen == 1 && vnode_name[0] != '0'))) > > > + return (ENOENT); > > > + if (vnode_namelen != endfileno - vnode_name) > > > + return (ENOENT); > > > + > > > + fdp = fdhold(p); > > > + if (fdp == NULL) > > > + return (ENOENT); > > > + > > > + error = fget_unlocked(fdp, fileno, NULL, &fp, NULL); > > > + if (error != 0) > > > + goto out; > > > + > > > + freepath = NULL; > > > + fullpath = "-"; > > > + vp = fp->f_vnode; > > > + if (vp != NULL) { > > > + vref(vp); > > > + error = vn_fullpath(td, vp, &fullpath, &freepath); > > > + vrele(vp); > > > + } > > > + if (error == 0) > > > + error = sbuf_printf(sb, "%s", fullpath); > > > + if (freepath != NULL) > > > + free(freepath, M_TEMP); > > > + fdrop(fp, td); > > > + > > > + out: > > > + fddrop(fdp); > > > + return (error); > > > +} > > > > > > > > > fdhold does not protect file descriptor table, it only makes sure struct > > filedesc itself is not freed. > > > > Here you need to lock it and inspect fd_refcnt. See e.g. > > kern_proc_filedesc_out. > > > pfs_readlink does a PHOLD and PRELE around calling fill method, is > this not enought? > This does not prevent execve, so you can dump data for a now-privileged process. > > While this guarantees data consistency, is in fact still incorrect since > > the process you are inspecing can exec setuid in the meantime and thus > > make security checks (if any performed) stale. > > > > I have an old WIP patch which provides appropriate interfaces to ensure > > stability of the process (no exit, no exec), but this needs additional > > changes. HOpefully i'll have the time to deal with it in March. > ok, give me see the patch, pls. http://people.freebsd.org/~mjg/patches/sx-imagelock.patch afair there was a lor which needs to be resolved. something in devfs was taking proctree or allproc lock, which could be avoided. I don't remember the details, maybe i'll work on this this month. Feel free to debug it yourslef. :) -- Mateusz Guzik <mjguzik gmail.com>
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