Version: rsync-3.2.6-1.1.x86_64 from OpenSuSE Tumbleweed, get it from
https://download.opensuse.org/repositories/openSUSE:/Factory/standard/x86_64/rsync-3.2.6-1.1.x86_64.rpm
(or .src.rpm).

Symptom: In certain circumstances (see the reproducer script), rsync
from a remote source to a local destination and using a --files-from list sometimes rejects an implicit containing directory with this error message:
    ERROR: rejecting unrequested file-list name: usr/lib64
    rsync error: protocol incompatibility (code 2) at flist.c(998) \
          [Receiver=3.2.6]

Success or failure depends on arcane determinstic variations, and there
is a suspicion that the same input might produce different output at
different times.  However, I repeated two variants 20 times a few secs
apart and they always worked or failed.

I've found these variant behaviors:
* With either sender version, receiver 3.2.5 always works and 3.2.6
  sometimes fails.
* If both the source and destination are local, it always works.
* If the destination is remote, it works.  Failures are seen with a
  remote source.
* All my test cases have two implicit containing directories.
  The first one has never been seen to fail but the second one does.
  I haven't investigated if third or subsequent dirs would fail.
  In one case where the second dir failed, exchanging the two filenames
  led to both of them succeeding.
* I'm using rsync in a configuration management system and it needs some
  options.  If I remove -K -O --numeric-ids leaving only --rsh=ssh -a
  --files-from, it fails or works equally.
* If I add --trust-sender then failing cases start working.

v3.2.5 has an addition to recognize if a rogue sender adds unrequested
toplevel names etc.  (CVE-2022-29154)  The option --trust-sender
disables the new paranoia.  If this option is added to the execution
command line, spurious rejections disappear.  Clearly the bugfixes in
file-list processing added in v3.2.6 had a bad interaction with the new
paranoia.

Attaching reproducer script rsyncbug.sh .

--
James F. Carter   Email: j...@jfcarter.net
Web: http://www.math.ucla.edu/~jimc (q.v. for PGP key)
#!/bin/bash
# rsync-3.2.6-1.1.x86_64 shows the bug; rsync-3.2.5-1.1.x86_64 works perfectly.
# The --files-from list has just files, but one of the implicit containing
# directories will be rejected with this error message:
#    ERROR: rejecting unrequested file-list name: usr/lib64
#    rsync error: protocol incompatibility (code 2) at flist.c(998) \
#	  [Receiver=3.2.6]
# Receiver 3.2.5 works with either sender.  Receiver 3.2.6 fails with either.
# Not every --files-from list sets off the bug.  

: ${HOSTNAME:=$(uname -n)}	# Name of this host for "remote" execution
j=/var/tmp/root.jimc		# Directory to put the test files in
mkdir -p $j
cd $j

# Actual filenames that failed in the config management system
if /bin/true ; then			# *** Turn on one of these
cat - > $j/filesfrom.ls <<EOF
usr/lib/security/pam_runscript.so
usr/lib/security/pam_runscript.so.i586
usr/lib64/mesa/bin/data
usr/lib64/sasl2/cgi-helper
usr/lib64/sasl2/cgi-helper.x86_64
usr/lib64/security/pam_runscript.so
usr/lib64/security/pam_runscript.so.x86_64
EOF
fi
# Simplified filenames for reproducer.  
if /bin/false ; then			# *** Turn on one of these
cat - > $j/filesfrom.ls <<EOF
lib/testlib.txt
lib64/testoib64.txt
EOF
fi

# Sets up the source content.  The destination is created implicitly.  Fails 
# or succeeds equally whether or not dst already exists.  
rm -rf $j/{src,dst}
while read fname junk ; do
    fname=$j/src/$fname
    mkdir -p ${fname%/*}
    echo "Test File $fname" > $fname
done < $j/filesfrom.ls

# Testing rsync...
rsync --rsh=ssh	-a -K -O --numeric-ids --files-from=$j/filesfrom.ls $HOSTNAME:$j/src/ $j/dst/
echo "exit code = $?"

# Outcomes: 
# "rsync --options $j/src/ $j/dst/" works perfectly on either file list.
# "rsync --options $HOSTNAME:$j/src/ $j/dst/" rejects dirname of 2nd file
#	(lib/ OK, lib64/ rejected).  This order and remote src are used for 
#	variant tests except as noted.  
# But if lib64/ is before lib/ then both are transferred.  
# "rsync --options $j/src/ $HOSTNAME:$j/dst/" transfers both files. 
# Aargh, there's a suspicion that it may be intermittent!  Got to test a lot
# of repetitions.  These were a few seconds apart, using the actual filenames. 
# 1 = failed on first dir, 2 = failed on 2nd dir, x = transferred both files.  
#	x x x x x x x x x x x x x x x x x x x x x (21 trials, remote dst)
#	2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2   (20 trials, remote src)
# If most options are removed, leaving only --rsh=ssh -a --files-from, 
# it fails or succeeds equally.  Failed with orig. filenames, remote src,
# /usr/lib64 second.  Worked with simplified names.  

# Big clue!  v3.2.5 has an addition to recognize if a rogue sender adds 
# unrequested toplevel names etc.  (CVE-2022-29154)  The option --trust-sender
# disables the new paranoia.  If this option is added to the execution command
# line, spurious rejections disappear.  Clearly the bugfixes in file-list
# processing added in v3.2.6 had a bad interaction with the new paranoia.  
-- 
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