Date: Tue, 29 Aug 2023 21:12:05 +0300 From: Dmitry Chagin <dchagin@freebsd.org> To: current@freebsd.org Subject: Re: Possible issue with linux xattr support? Message-ID: <ZO409dM4Ws7x_yuM@heemeyer.club> In-Reply-To: <uvavvxn7vgjhf5fswoxcawuolvviq2idedxyt4fe6vtjlewsex@aqssespkdh4e> References: <ZOuNvisMH_GXHHX2@heemeyer.club> <pzu4sxp4wvfpn3mzzo2giw3otvg6z5ewia6rr2tdgpkjurfcfe@aat2k6ywm6jm> <ZOuoH6Llw8PKgMJQ@heemeyer.club> <wuwg3egv3rilgfaa5hor47v3yjwzvxlt5krj4la4wvugcnhkg3@vgrtgfr7rc6i> <EA27BAE1-C687-47F9-BB6D-B72A85A5CA8D@cschubert.com> <elx6cvceobzgw66fskkfhhicsdpsur5xaktluu5tk7m7p4qwno@s7qmm4kyuvag> <ZOzD9noXVrslppot@heemeyer.club> <smfbmu35sxh2f3hu5nrpdwb355trlucd2bbp4ag5ke7v3zf3il@s3ua2x4i3nzj> <ZO4En1UJqcr4GGiw@heemeyer.club> <uvavvxn7vgjhf5fswoxcawuolvviq2idedxyt4fe6vtjlewsex@aqssespkdh4e>
next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, Aug 29, 2023 at 07:02:22PM +0200, Felix Palmen wrote: > * Dmitry Chagin <dchagin@freebsd.org> [20230829 17:45]: > > On Tue, Aug 29, 2023 at 12:59:11PM +0200, Felix Palmen wrote: > > > Thanks, I can confirm this avoids the issue in both cases I experienced > > > (install from GNU coreutils and python). > > > > > thanks, this is the first half of the fix, it works for you due to you > > are running tools under unprivileged user, afaiu. The second I have > > tested by myself :) > > Sure, poudriere is running all builds as "nobody" by default. > > > > If I understand this patch correctly, it completely avoids EPERM, > > > masking it as not supported, so callers should consider it non-fatal, > > > allowing to silently ignore writing of "system" attributes while still > > > keeping other functionality? > > > > > system namespace is accessible only for privileged user, for others Linux > > returns ENOTSUP. So many tools ignores this error, eg ls. > > > > the second: https://people.freebsd.org/~dchagin/sea_jailed.patch > > Ok, I did some tests in a poudriere jail using Linux bash, as root. > First, with only the first patch: > > | bash-5.2# getfattr -d /bin/sh > | getfattr: /bin/sh: Operation not supported > | bash-5.2# setfattr -n user.foo -v bar /bin/sh > | bash-5.2# getfattr -n user.foo /bin/sh > | getfattr: Removing leading '/' from absolute path names > | # file: bin/sh > | user.foo="bar" > | bash-5.2# setfattr -x user.foo /bin/sh > | bash-5.2# setfattr -x system.foo /bin/sh > | setfattr: /bin/sh: Operation not supported > > So, using user.* works, using system.* doesn't, and maybe a bit > surprising(?), dumping all attributes which by default excludes the > system namespace doesn't work either. > As expected, the second patch intended to allow access to system namespace in jailed env. > Then with the second patch applied as well: > > | bash-5.2# getfattr -d /bin/sh > | bash-5.2# setfattr -n system.foo -v bar /bin/sh > | bash-5.2# getfattr -d /bin/sh -m- > | getfattr: Removing leading '/' from absolute path names > | # file: bin/sh > | system.foo="bar" > | > | bash-5.2# setfattr -x system.foo /bin/sh > | bash-5.2# getfattr -d /bin/sh -m- > | bash-5.2# > > This looks perfectly fine, thanks a lot! > > I still wonder, is the first patch needed anyways? Maybe I fail to > understand something here. Won't it map *every* EPERM to ENOSUP and > can't this be an issue? > fine, thanks. Gnu tools running under unprivileged user will fail, eg ls, which uses getfattr() to get the posix acl > Cheers, Felix > > -- > Felix Palmen <zirias@FreeBSD.org> {private} felix@palmen-it.de > -- ports committer -- {web} http://palmen-it.de > {pgp public key} http://palmen-it.de/pub.txt > {pgp fingerprint} 6936 13D5 5BBF 4837 B212 3ACC 54AD E006 9879 F231
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?ZO409dM4Ws7x_yuM>