openssh bugs - Nov 2008 - [Bug 1535] New: rename doesn't fall back to rename syscall upon ENOSYS of link syscall

https://bugzilla.mindrot.org/show_bug.cgi?id=1535

           Summary: rename doesn't fall back to rename syscall upon ENOSYS
                    of link syscall
           Product: Portable OpenSSH
           Version: 5.1p1
          Platform: ix86
        OS/Version: Linux
            Status: NEW
          Keywords: patch
          Severity: normal
          Priority: P3
         Component: sftp-server
        AssignedTo: unassigned-bugs at mindrot.org
        ReportedBy: johan.kielbaey at gmail.com


Currently renaming of a file is implemented via a link() and unlink()
syscall with the possibility to fall back to the rename() syscall in
certain conditions (ENOTSUPP etc).

In case the errorcode returned by link() is ENOSYS this is not the
case.

The attached patch implements a fallback to rename in case of ENOSYS.

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--- Comment #1 from Johan Kielbaey <johan.kielbaey at gmail.com> 
2008-11-07 08:38:43 ---
Created an attachment (id=1578)
 --> (http://bugzilla.mindrot.org/attachment.cgi?id=1578)
Patch fall back to rename() upon ENOSYS errorcode.

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Johan Kielbaey <johan.kielbaey at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |johan.kielbaey at gmail.com




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Darren Tucker <dtucker at zip.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dtucker at zip.com.au




--- Comment #2 from Darren Tucker <dtucker at zip.com.au>  2008-11-07
09:22:16 ---
Sounds reasonable, but under what conditions does link return ENOSYS? 
It's not documented in link(2) as a possible errno.

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |djm at mindrot.org
             Blocks|                            |1481




--- Comment #3 from Damien Miller <djm at mindrot.org>  2008-12-08
09:36:37 ---
We'd like this for openssh-5.2, but Darren's question needs an answer
before we can commit it.

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--- Comment #4 from Darren Tucker <dtucker at zip.com.au>  2008-12-09
11:39:57 ---
(In reply to comment #3)
> We'd like this for openssh-5.2, but Darren's question needs an
answer
> before we can commit it.
Actually that was covered over on openssh-unix-dev: it's sshfs that
returns ENOSYS.

http://marc.info/?l=openssh-unix-dev&m=122602218711487

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--- Comment #5 from Johan Kielbaey <johan.kielbaey at gmail.com> 
2008-12-09 23:28:14 ---
(In reply to comment #4)
It was also brought to my attention on the mailinglist that the syscall
link() shouldn't return ENOSYS. According to the link(2) the
implementation of link in sshfs should return EPERM to indicate that
creation of links is not supported. However the error check in
sftp-server doesn't check EPERM either.

So actually the proper solution would be to fix this in sshfs and to
add a fix in sftp-server to also check for EPERM.

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--- Comment #6 from Darren Tucker <dtucker at zip.com.au>  2008-12-10
10:07:37 ---
(In reply to comment #5)
> (In reply to comment #4)
> It was also brought to my attention on the mailinglist that the syscall
> link() shouldn't return ENOSYS. According to the link(2) the
> implementation of link in sshfs should return EPERM to indicate that
> creation of links is not supported. However the error check in
> sftp-server doesn't check EPERM either.
Actually it does (on Linux, anyway):

                if (link(oldpath, newpath) == -1) {
                        if (errno == EOPNOTSUPP
#ifdef EXDEV
                            || errno == EXDEV
#endif
#ifdef LINK_OPNOTSUPP_ERRNO
                            || errno == LINK_OPNOTSUPP_ERRNO
#endif
                            ) {


where on Linux, LINK_OPNOTSUPP_ERRNO is defined thusly:
        AC_DEFINE(LINK_OPNOTSUPP_ERRNO, EPERM,
                [Define to whatever link() returns for "not supported"
                if it doesn't return EOPNOTSUPP.])

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|1481                        |1560




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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


--- Comment #7 from Damien Miller <djm at mindrot.org> 2009-08-28 10:44:39
EST ---
patch applied - this will be in openssh-5.3

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED

--- Comment #8 from Damien Miller <djm at mindrot.org> 2009-10-06 15:01:59
EST ---
Mass move of RESOLVED bugs to CLOSED now that 5.3 is out.

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