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Date: Mon, 27 Oct 2008 14:00:05 -0700 From: Rob MacKinnon <c4blem0nkey@...il.com> To: Stephen Smalley <sds@...ho.nsa.gov> CC: rob.mackinnon@...il.com, Andreas Gruenbacher <agruen@...e.de>, hpa@...or.com, hugh@...itas.com, linux-kernel@...r.kernel.org, Casey Schaufler <casey@...aufler-ca.com> Subject: Re: tmpfs support of xattrs? Stephen Smalley wrote: > On Mon, 2008-10-27 at 13:14 -0700, Rob MacKinnon wrote: >> Andreas Gruenbacher wrote: >>> On Sunday, 26 October 2008 13:26:35 Hugh Dickins wrote: >>>> On Sat, 25 Oct 2008, Rob MacKinnon wrote: >>>>> The background: So during the initial configuration of a box I enabled >>>>> the xattr flags for ext3 and options of xattr in coreutils, and at the >>>>> time didn't realize that I'd hit a snag that would finally annoy me >>>>> enough after a month of getting a non-fatal error messages from cp "cp: >>>>> listing attributes of `/dev/null`: Invalid argument" to spend half a day >>>>> researching the cause and a potential solution. >>>>> >>>>> Setup: udev mounts a tmpfs to /dev then fills it with device nodes. >>>>> Problem: the resulting tmpfs has no xattr support. >>>>> Therefore: Tmpfs without xattrs, and coreutils and everywhere else with >>>>> xattr support, cp freaks. >>>>> >>>>> Is there sometime in the forseable future when the tmpfs module will >>>>> support for xattrs in the stable branch, or should I "holler at the >>>>> maintainers of coreutils to fix their broken code in cp". Even better >>>>> (and I like this option the most) a little of both? >>>> I've not seen "cp: listing attributes of `/dev/null': Invalid argument" >>>> messages (or.. do I have a dim recollection of them once upon a time?). >>>> I would certainly get irritated by them if I did, and want to fix them. >>>> I tried "cp /dev/null temp" on a few distros just now but not seen it. >>> As Hugh pointed out already, tmpfs does support xattrs since quite a while, so >>> enabling that should fix the symptoms. Independent of that, cp must of course >>> work correctly on filesystems that don't have xattrs. Those filesystems are >>> not supposed to return EINVAL, though. >>> >>> Could you please run cp under strace to show us what's happening at the >>> syscall level (and perhaps under ltrace in addition to see the library level >>> as well)? >>> >>> If the error happens at the syscall level (*listxattr), then which kernel is >>> it exactly, and where can I find its sources? >>> >> Thanks Andreas, Hugh & HPA >> >> First off, thanks for looking into this. After googling around, hitting >> forums and such and not getting any answers, this list seemed the best >> place to come to ask. >> >> Now onward to business...I can say that I too was under the general >> understanding that xattr for tmpfs was added at 2.6.10...and was still >> currently supported. Unfortunately I already have the config flags set >> (as seen below, for a full config set attached) so there is a continued >> confusion in my mind why this is still plaguing me. >> >> I've had several friends compare what was going on, and of them they >> were all running rhel and cent (most with no udev support so the >> comparison didn't help at all). >> >> I'll start out with distro info and the like... >> `uname -a`="Linux shin-yuko 2.6.26-gentoo-r2 #1 SMP PREEMPT Wed Oct 22 >> 16:31:40 PDT 2008 i686 Intel(R) Pentium(R) 4 CPU 2.80GHz GenuineIntel >> GNU/Linux" >> >> coreutils-version="coreutils-6.12-r2" >> >> My current config does have the following set: >> CONFIG_TMPFS=y >> CONFIG_TMPFS_POSIX_ACL=y >> CONFIG_SHMEM=y >> >> Output from `strace /bin/cp /dev/null /root/temp`= #see attachment >> Output from `ltrace -CS /bin/cp /dev/null /root/temp`= #see attachment >> >> Output from `attr -l /dev/null`=Segfault (hmmm...lemme look at a strace >> and ltrace of that too) >> >> `strace attr -l /dev/null`= #see attachment >> `ltrace -CS /bin/attr -l /dev/null`= #see attachment >> >> Kernel source can be attained from: >> http://distfiles.gentoo.org/distfiles/linux-2.6.26.tar.bz2 >> >> Patches: >> http://sources.gentoo.org/viewcvs.py/linux-patches/genpatches-2.6/trunk/2.6.26/ >> >> I know this is silly but, setfattr and getfattr obviously don't work >> either...just thought it was worth mentioning. > > Looks like a bug in Smack's implementation of the inode_listsecurity > hook to me. Did you mean to enable Smack in your kernel config? > I had intensionally flipped CONFIG_SECURITY_SMACK to "y". I'm used to running hardened with GRSec and RBAC (ot: but found the gentoo versioning was so far behind / and me being lazy and not wanting to manually do the patching / I dropped using hardened sources) so when I saw the option for what sounded like a good compromise I jumped at it. Looks like I did a good thing too having uncovered a problem. :) -- Rob -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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