[PATCH] selftests/lkdtm: Use "comm" instead of "diff" for dmesg

[Kees Cook]

Instead of full GNU diff (which smaller boot environments may not have),
use "comm" which is more available.

Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
Link: https://lore.kernel.org/lkml/CA+G9fYtHP+Gg+BrR_GkBMxu2oOi-_e9pATtpb6TVRswv1G1r1Q@xxxxxxxxxxxxxx
Fixes: f131d9edc29d ("selftests/lkdtm: Don't clear dmesg when running tests")
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 tools/testing/selftests/lkdtm/run.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/lkdtm/run.sh b/tools/testing/selftests/lkdtm/run.sh
index 8383eb89d88a..5fe23009ae13 100755
--- a/tools/testing/selftests/lkdtm/run.sh
+++ b/tools/testing/selftests/lkdtm/run.sh
@@ -82,7 +82,7 @@ dmesg > "$DMESG"
 ($SHELL -c 'cat <(echo '"$test"') >'"$TRIGGER" 2>/dev/null) || true
 
 # Record and dump the results
-dmesg | diff --changed-group-format='%>' --unchanged-group-format='' "$DMESG" - > "$LOG" || true
+dmesg | comm -13 "$DMESG" - > "$LOG" || true
 
 cat "$LOG"
 # Check for expected output
-- 
2.25.1


-- 
Kees Cook