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On 2020-08-17T16:13:21+00:00 Ldv-c wrote:

Fixes for https://sourceware.org/bugzilla/show_bug.cgi?id=14578
introduced regressions in cases when /proc is not mounted:
- lchmod used to return ENOSYS, now it returns EOPNOTSUPP;
- fchmodat(AT_SYMLINK_NOFOLLOW) used to return ENOTSUP, now it returns 
EOPNOTSUPP which is different from ENOTSUP on some architectures, e.g. hppa.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/rsync/+bug/1902109/comments/0

------------------------------------------------------------------------
On 2020-10-30T07:31:47+00:00 Alkis Georgopoulos wrote:

Hello, just noting that rsync in Ubuntu 20.10 is affected by this glibc
issue:

https://bugs.launchpad.net/ubuntu/+source/rsync/+bug/1902109
https://github.com/WayneD/rsync/issues/109

Reply at:
https://bugs.launchpad.net/ubuntu/+source/rsync/+bug/1902109/comments/4


** Changed in: glibc
       Status: Unknown => Confirmed

** Changed in: glibc
   Importance: Unknown => Medium

** Bug watch added: Sourceware.org Bugzilla #14578
   https://sourceware.org/bugzilla/show_bug.cgi?id=14578

** Bug watch added: github.com/WayneD/rsync/issues #109
   https://github.com/WayneD/rsync/issues/109

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https://bugs.launchpad.net/bugs/1902109

Title:
  rsync uses lchmod and fails in Ubuntu >= 20.10 if /proc isn't mounted

Status in GLibC:
  Confirmed
Status in glibc package in Ubuntu:
  New
Status in rsync package in Ubuntu:
  Triaged

Bug description:
  Rsync in Ubuntu 20.10 fails when /proc isn't mounted, while it worked before.
  This happens because AC_CHECK_FUNC(lchmod) returns "yes" in 20.10, while it 
returned "no" before.

  Steps to reproduce:

  # Emulate /proc not being mounted
  $ mount --bind / /mnt
  $ chroot /mnt rsync -a /bin/ls .
  rsync: [receiver] failed to set permissions on "/.ls.CDExhu": Operation not 
supported (95)
  rsync error: some files/attrs were not transferred (see previous errors) 
(code 3) at main.c(1330) [sender=3.2.3]

  I reported this issue upstream in
  https://github.com/WayneD/rsync/issues/109 but the rsync developer
  says it's a problem in libc, and it might well be.

  Simple C code to reproduce the problem without rsync:

  printf("lchmod returned: %d\n", lchmod("/tmp/ls", 0755));

  If /tmp/ls is e.g. mode=0123, and needs to be changed, lchmod fails
  when /proc isn't mounted, yet it succeeds if it is mounted.

  Python had a similar issue, and they ended up avoiding
  AC_CHECK_FUNC(lchmod) under Linux:

  https://bugs.python.org/issue34652
  
https://github.com/python/cpython/commit/69e96910153219b0b15a18323b917bd74336d229#diff-49473dca262eeab3b4a43002adb08b4db31020d190caaad1594b47f1d5daa810R3140

  ```c
  if test "$MACHDEP" != linux; then
    AC_CHECK_FUNC(lchmod)
  fi
  ```

  So I'm not sure which package is causing the bug here. Should autoconf
  return false? Should libc implement lchown without the bug? Or should
  rsync skip lchmod under Linux, like python did?

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