On Thu, Oct 7, 2010 at 3:36 AM, Alexander Best <arun...@freebsd.org> wrote: > On Wed Oct 6 10, Garrett Cooper wrote: >> On Wed, Oct 6, 2010 at 4:03 PM, Garrett Cooper <gcoo...@freebsd.org> wrote: >> > On Wed, Oct 6, 2010 at 3:01 PM, Sergey Kandaurov <pluk...@gmail.com> wrote: >> >> On 6 October 2010 23:38, Alexander Best <arun...@freebsd.org> wrote: >> >>> On Wed Oct 6 10, Garrett Cooper wrote: >> >>>> On Wed, Oct 6, 2010 at 10:35 AM, Alexander Best <arun...@freebsd.org> >> >>>> wrote: >> >>>> > On Wed Oct 6 10, Garrett Cooper wrote: >> >>>> >> On Tue, Oct 5, 2010 at 4:50 PM, Alexander Best <arun...@freebsd.org> >> >>>> >> wrote: >> >>>> >> > hi there, >> >>>> >> > >> >>>> >> > i think the following example shows the problem better than a long >> >>>> >> > explanation: >> >>>> >> > >> >>>> >> > `touch ftest && chflags arch ftest && chflags -vv 0 ftest`. >> >>>> >> > ^^non-root ^^root ^^non-root >> >>>> >> > >> >>>> >> > chflags claims to have cleared the 'arch' flag (which should be >> >>>> >> > impossible as >> >>>> >> > non-root user), but indeed has done nothing. >> >>>> >> > >> >>>> >> > i've tried the same with 'sappnd' and that works as can be >> >>>> >> > expected. >> >>>> >> > >> >>>> >> > The issue was confirmed to exist in HEAD (me), stable/8 >> >>>> >> > (pgollucc1, jpaetzel) >> >>>> >> > and stable/7 (nox). >> >>>> >> > On stable/6 it does NOT exist (jpaetzel). chflags properly fails >> >>>> >> > with EPERM. >> >>>> >> >> >>>> >> Fails for me when I call the syscall directly, as I would expect, >> >>>> >> and passes when I'm superuser: >> >>>> >> >> >>>> >> $ ./test_chflags >> >>>> >> (uid, euid) = (1000, 1000) >> >>>> >> test_chflags: chflags: Operation not permitted >> >>>> >> test_chflags: lchflags: Operation not permitted >> >>>> >> $ sudo ./test_chflags >> >>>> >> (uid, euid) = (0, 0) >> >>>> >> >> >>>> >> According to my basic inspection in strtofflags >> >>>> >> (.../lib/libc/gen/strtofflags.c), it works as well. >> >>>> >> And last but not least, executing the commands directly on the >> >>>> >> CLI work: >> >>>> >> >> >>>> >> $ tmpfile=`mktemp /tmp/chflags.XXXXXX` >> >>>> >> $ chflags arch $tmpfile >> >>>> >> chflags: /tmp/chflags.nQm1IL: Operation not permitted >> >>>> >> $ rm $tmpfile >> >>>> >> $ tmpfile=`mktemp /tmp/chflags.XXXXXX` >> >>>> >> $ sudo chflags arch $tmpfile >> >>>> >> $ sudo chflags noarch $tmpfile >> >>>> >> $ rm $tmpfile >> >>>> > >> >>>> > thanks for your test app and helping out with this problem. i'm not >> >>>> > sure >> >>>> > however you understood the problem. probably i didn't explain it >> >>>> > right: >> >>>> > >> >>>> > $ sudo rm -d /tmp/chflags.XXXXXX >> >>>> > $ tmpfile=`mktemp /tmp/chflags.XXXXXX` >> >>>> > $ sudo chflags arch $tmpfile >> >>>> > $ chflags noarch $tmpfile >> >>>> > >> >>>> > is what's causing the problem. the last chflags call should fail, but >> >>>> > it >> >>>> > doesn't. >> >>>> >> >>>> Sorry... my CLI based example was stupid. I meant: >> >>>> >> >>>> $ tmpfile=`mktemp /tmp/chflags.XXXXXX` >> >>>> $ chflags arch $tmpfile >> >>>> chflags: /tmp/chflags.V2NpXR: Operation not permitted >> >>>> $ chflags noarch $tmpfile >> >>>> $ rm $tmpfile >> >>>> >> >>>> Currently chflags(2) states: >> >>>> >> >>>> The SF_IMMUTABLE, SF_APPEND, SF_NOUNLINK, and SF_ARCHIVED flags >> >>>> may only >> >>>> be set or unset by the super-user. Attempts to set these flags by >> >>>> non- >> >>>> super-users are rejected, >>> attempts by non-superusers to clear >> >>>> flags that >> >>>> are already unset are silently ignored. <<< These flags may be >> >>>> set at any >> >>>> time, but normally may only be unset when the system is in >> >>>> single-user >> >>>> mode. (See init(8) for details.) >> >>>> >> >>>> So this behavior is already well documented :). The EPERM section >> >>>> should really note SF_ARCHIVED though (whoever added the flag forgot >> >>>> to add that particular item to the ERRORS section). >> >>> >> >>> that's perfectly alright. clearing an unset flag shouldn't cause any >> >>> error to >> >>> be returned. however in my example arch *does* get set and still trying >> >>> to >> >>> unset it as normal user doesn't return an error. >> >>> >> >> >> >> It's even more interesting. >> >> >> >> As far as I could parse the code: >> >> - UFS has no special handling for SF_ARCHIVED (I found only it for >> >> msdosfs) >> > >> > _very_ interesting: >> > >> > [/sys]$ grep -r SF_ARCHIVED kern/ fs/ ufs/ | grep -v svn >> > fs/msdosfs/msdosfs_vnops.c: vap->va_flags |= SF_ARCHIVED; >> > fs/msdosfs/msdosfs_vnops.c: if (vap->va_flags & ~SF_ARCHIVED) >> > fs/msdosfs/msdosfs_vnops.c: if (vap->va_flags & SF_ARCHIVED) >> > >> > The commit that introduced this change probably wasn't doing the >> > right thing: >> > http://svn.freebsd.org/viewvc/base/head/sys/fs/msdosfs/msdosfs_vnops.c?revision=5241&view=markup >> > ; cp(1) probably should have been fixed in lieu of `fixing' msdosfs. >> > >> >> - ufs_setattr() does not handle unsetting SF_ARCHIVED, >> >> so all what it does is simply return zero. >> > >> > [EOPNOTSUPP] The underlying file system does not support file >> > flags. >> > >> > So I would expect for invalid flags to return EOPNOTSUPP. >> > >> > ... >> > >> > $ ~/test_chflags_negative >> > test_chflags_negative: should not get here >> > $ sudo ~/test_chflags_negative >> > test_chflags_negative: should not get here >> > >> > *facepalm* >> > >> > I think the problem in part is here (sys/stat.h): >> > >> > * >> > * Super-user and owner changeable flags. >> > */ >> > #define UF_SETTABLE 0x0000ffff /* mask of owner changeable flags >> > */ >> > #define UF_NODUMP 0x00000001 /* do not dump file */ >> > #define UF_IMMUTABLE 0x00000002 /* file may not be changed */ >> > #define UF_APPEND 0x00000004 /* writes to file may only append >> > */ >> > #define UF_OPAQUE 0x00000008 /* directory is opaque wrt. union >> > */ >> > #define UF_NOUNLINK 0x00000010 /* file may not be removed or >> > renamed */ >> > /* >> > * Super-user changeable flags. >> > */ >> > #define SF_SETTABLE 0xffff0000 /* mask of superuser changeable >> > flags */ >> > #define SF_ARCHIVED 0x00010000 /* file is archived */ >> > #define SF_IMMUTABLE 0x00020000 /* file may not be changed */ >> > #define SF_APPEND 0x00040000 /* writes to file may only append >> > */ >> > #define SF_NOUNLINK 0x00100000 /* file may not be removed or >> > renamed */ >> > #define SF_SNAPSHOT 0x00200000 /* snapshot inode */ >> > >> > Note the *_SETTABLE macros, and the fact that they allow for more >> > functionality than what's currently slotted with the one-hot encoded >> > flags currently available. >> > SF_ARCHIVED is not present in the other BSDs or Mac OSX either (I >> > did some hunting for a python bug related to chflags a few weeks >> > ago)... and I'm not even sure what this functionality really buys us >> > because it's not well described (but I'd be happy to get an >> > explanation/history lesson). >> > >> >> - /bin/chflags doesn't check the actual flags value from inode after >> >> calling chflags() syscall, and blindly assumes all is well, if chflags() >> >> returns with zero, >> > >> > Yeah... but ideally tests should be written for this stuff and >> > exercised on all filesystems and exercised whenever code in this >> > particular path is changed, because that would potentially turn into a >> > noticeable performance hit [depending on how it's implemented in >> > chflags(1)]. And lo and behold it already does exist under >> > .../tools/regression/fstest/tests/chflags . I'll audit this once I get >> > back home... >> >> For starters, the tests were moved to .../tools/regression/pjdfstest . >> This fixes the manpage and the negative flags testcase at least. I >> ran the pjdfstest on a UFS2 partition on my test machine and tmpfs, >> and it passed chflags with flying colors. msdosfs unfortunately isn't >> supported yet, but I did some manual testing and everything seemed ok. >> I also need to check and see whether or not pjdfstest is doing the >> right job with negative testcases. >> I didn't have a ext2/3 or zfs pool to test with, so if someone >> could poke around with those filesystems it would be much appreciated >> :). >> And finally, here are all of the references in the sourcebase to >> SF_ARCHIVED: >> >> # /usr/local/bin/svnversion >> 213377M >> # grep -r SF_ARCHIVED /usr/src/ | grep -v svn >> grep: >> /usr/src/tools/regression/pjdfstest/pjdfstest_5aaec5b222b60945b16daa0e8d61313d/pjdfstest_b4353ca81458e0bfc9ec5be8ff741eb2/usr/src/tools/regression/priv/priv_vfs_chflags.c: >> flags >> |= SF_ARCHIVED; >> /usr/src/tools/regression/priv/priv_vfs_chflags.c: flags |= SF_ARCHIVED; >> /usr/src/tools/regression/priv/priv_vfs_chflags.c: flags |= SF_ARCHIVED; >> /usr/src/tools/regression/pjdfstest/tests/chflags/00.t: >> allflags="UF_NODUMP,UF_IMMUTABLE,UF_APPEND,UF_NOUNLINK,UF_OPAQUE,SF_ARCHIVED,SF_IMMUTABLE,SF_APPEND,SF_NOUNLINK" >> /usr/src/tools/regression/pjdfstest/tests/chflags/00.t: >> systemflags="SF_ARCHIVED,SF_IMMUTABLE,SF_APPEND,SF_NOUNLINK" >> Binary file /usr/src/tools/regression/pjdfstest/pjdfstest matches >> /usr/src/tools/regression/pjdfstest/pjdfstest.c:#ifdef SF_ARCHIVED >> /usr/src/tools/regression/pjdfstest/pjdfstest.c: { SF_ARCHIVED, >> "SF_ARCHIVED" }, >> : Operation not supported >> grep: warning: /usr/src/sys/modules/tmpfs/@: recursive directory loop >> /usr/src/lib/libc/gen/strtofflags.c: { "noarch", SF_ARCHIVED, >> 0 }, >> /usr/src/lib/libc/gen/strtofflags.c: { "noarchived", SF_ARCHIVED, >> 0 }, >> /usr/src/lib/libc/sys/chflags.2:.It Dv SF_ARCHIVED >> /usr/src/lib/libc/sys/chflags.2:.Dv SF_ARCHIVED >> /usr/src/lib/libc/sys/chflags.2:.Dv SF_ARCHIVED , SF_IMMUTABLE , SF_APPEND , >> /usr/src/lib/libc/sys/chflags.2:.Dv SF_ARCHIVED , SF_IMMUTABLE , SF_APPEND , >> /usr/src/lib/libarchive/archive_entry.c:#ifdef SF_ARCHIVED >> /usr/src/lib/libarchive/archive_entry.c: { >> "noarch", L"noarch", SF_ARCHIVED, 0 }, >> /usr/src/lib/libarchive/archive_entry.c: { >> "noarchived", L"noarchived", SF_ARCHIVED, 0 }, >> /usr/src/sys/fs/msdosfs/msdosfs_vnops.c: vap->va_flags |= >> SF_ARCHIVED; >> /usr/src/sys/fs/msdosfs/msdosfs_vnops.c: if (vap->va_flags & >> ~SF_ARCHIVED) >> /usr/src/sys/fs/msdosfs/msdosfs_vnops.c: if (vap->va_flags & >> SF_ARCHIVED) >> /usr/src/sys/sys/stat.h:#define SF_ARCHIVED 0x00010000 /* >> file is archived */ >> /usr/src/sys/sys/stat.h:#define SF_SETTABLE (SF_ARCHIVED | >> SF_IMMUTABLE | SF_APPEND | \ >> >> So it doesn't look like anything's utilizing the functionality, >> other than msdosfs, and all that really does is tweak the following >> attribute: >> >> #define ATTR_ARCHIVE 0x20 /* file is new or modified */ >> >> and vice versa. I vaguely remember archive file types in FAT32 >> from the Win95 days, but my memory is a bit hazy as to what the >> attribute actually does. > > occasionally i get errors during file copies from msdosfs to ufs2. windows > seems to use the arch flag quite extensively actually. i think formating a new > drive automatically markes it as 'archivable' and all new files get their flag > set.
According to sbruno@: "It gets set when a file is written to. That's it. A backup program can backup files then clear the bit; later backups can use the state of the bit to determine if the file needs backing up again. And it dates from MS-DOS 2.x, and possibly even 1.x. During those times you couldn't exactly trust timestamps on files meant anything for backup purposes, as PCs didn't have a battery backed RTC as standard. http://en.wikipedia.org/wiki/Archive_bit" So it exists purely for msdosfs for that historic reason. > so when copying files from fat32 to ufs i very often get an EPERM error, > because as a non-root user that flag cannot be preserved. doesn't matter > however since the copying suceeds. good thing the chflags operation takes > place > after copying the file and not beforehand (i.e. touch, chflags, copy). Yeah... > also: what about sorting the flags (in the manual page e.g.). should they be > sorted alphabetically or by bitfields? They're currently sorted by value (including the patch I attached earlier). > also: is SF_SNAPSHOT really changeable by the super user? chflags(2) says it's > not. >From what I've seen, not directly. It's used widely in querying filesystems though. Thanks, -Garrett _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"