FAILED: patch "[PATCH] selftests: mptcp: join: avoid using 'cmp --bytes'" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x d328fe87067480cf2bd0b58dab428a98d31dbb7e
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2023060758-corset-cramp-8d97@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d328fe87067480cf2bd0b58dab428a98d31dbb7e Mon Sep 17 00:00:00 2001
From: Matthieu Baerts <matthieu.baerts@tessares.net>
Date: Sun, 28 May 2023 19:35:26 +0200
Subject: [PATCH] selftests: mptcp: join: avoid using 'cmp --bytes'

BusyBox's 'cmp' command doesn't support the '--bytes' parameter.

Some CIs -- i.e. LKFT -- use BusyBox and have the mptcp_join.sh test
failing [1] because their 'cmp' command doesn't support this '--bytes'
option:

    cmp: unrecognized option '--bytes=1024'
    BusyBox v1.35.0 () multi-call binary.

    Usage: cmp [-ls] [-n NUM] FILE1 [FILE2]

Instead, 'head --bytes' can be used as this option is supported by
BusyBox. A temporary file is needed for this operation.

Because it is apparently quite common to use BusyBox, it is certainly
better to backport this fix to impacted kernels.

Fixes: 6bf41020b72b ("selftests: mptcp: update and extend fastclose test-cases")
Cc: stable@vger.kernel.org
Link: https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.3-rc5-5-g148341f0a2f5/testrun/16088933/suite/kselftest-net-mptcp/test/net_mptcp_userspace_pm_sh/log [1]
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 26310c17b4c6..4f3fe45f8f71 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -17,6 +17,7 @@ sout=""
 cin=""
 cinfail=""
 cinsent=""
+tmpfile=""
 cout=""
 capout=""
 ns1=""
@@ -175,6 +176,7 @@ cleanup()
 {
 	rm -f "$cin" "$cout" "$sinfail"
 	rm -f "$sin" "$sout" "$cinsent" "$cinfail"
+	rm -f "$tmpfile"
 	rm -rf $evts_ns1 $evts_ns2
 	cleanup_partial
 }
@@ -383,9 +385,16 @@ check_transfer()
 			fail_test
 			return 1
 		fi
-		bytes="--bytes=${bytes}"
+
+		# note: BusyBox's "cmp" command doesn't support --bytes
+		tmpfile=$(mktemp)
+		head --bytes="$bytes" "$in" > "$tmpfile"
+		mv "$tmpfile" "$in"
+		head --bytes="$bytes" "$out" > "$tmpfile"
+		mv "$tmpfile" "$out"
+		tmpfile=""
 	fi
-	cmp -l "$in" "$out" ${bytes} | while read -r i a b; do
+	cmp -l "$in" "$out" | while read -r i a b; do
 		local sum=$((0${a} + 0${b}))
 		if [ $check_invert -eq 0 ] || [ $sum -ne $((0xff)) ]; then
 			echo "[ FAIL ] $what does not match (in, out):"