Date: Thu, 28 Feb 2013 19:58:51 -0500 (EST) From: Rick Macklem <rmacklem@uoguelph.ca> To: Konstantin Belousov <kostikbel@gmail.com> Cc: FreeBSD Filesystems <freebsd-fs@freebsd.org>, Sergey Kandaurov <pluknet@freebsd.org> Subject: Re: should vn_fullpath1() ever return a path with "." in it? Message-ID: <1208475167.3432384.1362099531469.JavaMail.root@erie.cs.uoguelph.ca> In-Reply-To: <20130228070515.GK2454@kib.kiev.ua>
next in thread | previous in thread | raw e-mail | index | archive | help
Kostik Belousov wrote: > On Wed, Feb 27, 2013 at 09:59:22PM -0500, Rick Macklem wrote: > > Hi, > > > > Sergey Kandaurov reported a problem where getcwd() returns a > > path with "/./" imbedded in it for an NFSv4 mount. This is > > caused by a mount point crossing on the server when at the > > server's root because vn_fullpath1() uses VV_ROOT to spot > > mount point crossings. > > > > The current workaround is to use the sysctls: > > debug.disablegetcwd=1 > > debug.disablefullpath=1 > > > > However, it would be nice to fix this when vn_fullpath1() > > is being used. > > > > A simple fix is to have vn_fullpath1() fail when it finds > > "." as a directory match in the path. When vn_fullpath1() > > fails, the syscalls fail and that allows the libc algorithm > > to be used (which works for this case because it doesn't > > depend on VV_ROOT being set, etc). > > > > So, I am wondering if a patch (I have attached one) that > > makes vn_fullpath1() fail when it matches "." will break > > anything else? (I don't think so, since the code checks > > for VV_ROOT in the loop above the check for a match of > > ".", but I am not sure?) > > > > Thanks for any input w.r.t. this, rick > > > --- kern/vfs_cache.c.sav 2013-02-27 20:44:42.000000000 -0500 > > +++ kern/vfs_cache.c 2013-02-27 21:10:39.000000000 -0500 > > @@ -1333,6 +1333,20 @@ vn_fullpath1(struct thread *td, struct v > > startvp, NULL, 0, 0); > > break; > > } > > + if (buf[buflen] == '.' && (buf[buflen + 1] == '\0' || > > + buf[buflen + 1] == '/')) { > > + /* > > + * Fail if it matched ".". This should only happen > > + * for NFSv4 mounts that cross server mount points. > > + */ > > + CACHE_RUNLOCK(); > > + vrele(vp); > > + numfullpathfail1++; > > + error = ENOENT; > > + SDT_PROBE(vfs, namecache, fullpath, return, > > + error, vp, NULL, 0, 0); > > + break; > > + } > > buf[--buflen] = '/'; > > slash_prefixed = 1; > > } > > I do not quite understand this. Did the dvp (parent) vnode returned by > VOP_VPTOCNP() equal to vp (child) vnode in the case of the "." name ? > It must be, for the correct operation, but also it should cause the > almost > infinite loop in the vn_fullpath1(). The loop is not really infinite > due > to a limited size of the buffer where the infinite amount of "./" is > placed. > > Anyway, I think we should do better than this patch, even if it is > legitimate. I think that the better place to check the condition is > the > default implementation of VOP_VPTOCNP(). Am I right that this is where > it broke for you ? > > diff --git a/sys/kern/vfs_default.c b/sys/kern/vfs_default.c > index 00d064e..1dd0185 100644 > --- a/sys/kern/vfs_default.c > +++ b/sys/kern/vfs_default.c > @@ -856,8 +856,12 @@ vop_stdvptocnp(struct vop_vptocnp_args *ap) > error = ENOMEM; > goto out; > } > - bcopy(dp->d_name, buf + i, dp->d_namlen); > - error = 0; > + if (dp->d_namlen == 1 && dp->d_name[0] == '.') { > + error = ENOENT; > + } else { > + bcopy(dp->d_name, buf + i, dp->d_namlen); > + error = 0; > + } > goto out; > } > } while (len > 0 || !eofflag); Yes, this patch fixes the problem too. If you think it is safe to do this, I can commit the patch in mid-April. Maybe Sergey can test it? Thanks yet again, rick
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?1208475167.3432384.1362099531469.JavaMail.root>