Date: Tue, 19 May 2020 10:37:45 -0500 From: Kyle Evans <kevans@freebsd.org> To: "Rodney W. Grimes" <rgrimes@freebsd.org> Cc: src-committers <src-committers@freebsd.org>, svn-src-all <svn-src-all@freebsd.org>, svn-src-head <svn-src-head@freebsd.org> Subject: Re: svn commit: r361238 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs Message-ID: <CACNAnaE-x2Y6rWJFMeS7_Tact3_FpahdAR1kaXtr-K70FhgURA@mail.gmail.com> In-Reply-To: <202005191534.04JFYlSQ006759@gndrsh.dnsmgr.net> References: <CACNAnaEJJ%2BbSWi8dU48i1s5a-rZTCKtc9OcQLZpx=Q3kN5Dryg@mail.gmail.com> <202005191534.04JFYlSQ006759@gndrsh.dnsmgr.net>
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On Tue, May 19, 2020 at 10:34 AM Rodney W. Grimes <freebsd@gndrsh.dnsmgr.net> wrote: > > > On Tue, May 19, 2020 at 10:27 AM Rodney W. Grimes > > <freebsd@gndrsh.dnsmgr.net> wrote: > > > > > > > On Tue, May 19, 2020 at 10:23 AM Rodney W. Grimes > > > > <freebsd@gndrsh.dnsmgr.net> wrote: > > > > > > > > > > > Author: kevans > > > > > > Date: Tue May 19 02:41:05 2020 > > > > > > New Revision: 361238 > > > > > > URL: https://svnweb.freebsd.org/changeset/base/361238 > > > > > > > > > > > > Log: > > > > > > zfs: reject read(2) of a dirfd with EISDIR > > > > > > > > > > > > This is independent of the recently-discussed global change, which is still > > > > > > in review/discussion stage. > > > > > > > > > > > > This is effectively a measure for consistency in the ZFS world, where > > > > > > FreeBSD was the only platform (as far as I could find) that allowed this. > > > > > > What ZFS exposes is decidedly not useful for any real purposes, to > > > > > > paraphrase (hopefully faithfully) jhb's findings when exploring this: > > > > > > > > > > > > The size of a directory in ZFS is the number of directory entries within. > > > > > > When reading a directory, you would instead get the leading part of its raw > > > > > > contents; the amount you get being dictated by the "size," i.e. number of > > > > > > directory entries. There's decidedly (luckily) no stack disclosure happening > > > > > > here, though the behavior is bizarre and almost certainly a historical > > > > > > accident. > > > > > > > > > > > > This change has already been upstreamed to OpenZFS. > > > > > > > > > > Until the grep -d skip issue is addressed I object to this change as > > > > > it is going to cause people who do grep with wildcards to see lots > > > > > of errors that before where pretty much either silent (no match occured) > > > > > or spit out a "binary file foo matches." > > > > > > > > > > > > > That seems preferable to grepping random bytes that don't particularly > > > > contain any strings? They'd never see "binary file foo matches" in > > > > this case. > > > > > > The difference is you rarely get a hit, and now your gauranteed to > > > get a hit on every single directory making grep * very noisy, where > > > it was often silent or nearly silent before. > > > > > > > As you noted in the review for the larger change, -d skip is a good > > option for the people that don't like this. It probably makes sense as > > a default, but then we'd be diverging from the other popular grep that > > defaults to -d read and spews out EISDIR more often than not. > > Yet another thing I hate about Linux, thank you for adding it to FreeBSD :-) > > > > > > > > > This isn't exactly divergent from the behavior they'd see with ZFS > > > > anywhere else. > > > > > > It is extremly divergent from 42 years of behavior. > > > > > > > I don't think ZFS has been implemented on FreeBSD for 42 years, and I > > don't find this grep argument compelling enough to restore peoples' > > ability to read the raw znode of a directory. > > The EISDIR behavior is what your changing, independent of file system(s) > you have done so far. The fact the behavior is now different between > UFS and ZFS is sic, IMHO. EISDIR in read(2) denotes that a filesystem does not support reading a directory, this isn't a new kind of error. In particular, ZFS traditionally does NOT support reading a directory like this. The behavior between UFS and ZFS should have always been different, this is correction of a historical *accident*.
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