(In reply to Dmitry V. Levin from comment #4)
> Just letting you know that we reverted commit
> 6b89c385d8bd0700b25bac2c2d0bebe68d5cc05d in our glibc build shortly after
> reporting this issue.
Reading rsync bug report, I really think that EOPNOTSUPP is the correct
error code to return in this case. The configure was done on a build
system where lchmod does work (since it has procps mounted). So I do not
fully agree this really characterizes as a regression.
And I don't think reverting lchmod support since propcs might be not
available is the correct approach, best option would try to ask kernel
to have proper syscall support which does not require userland hacks.
Rick Felker already sent a patch, but it seems to be stuck.
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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:
Invalid
Status in rsync package in Ubuntu:
Triaged
Status in glibc source package in Groovy:
Invalid
Status in rsync source package in Groovy:
Won't Fix
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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