dh_strip: Avoid potential unsafe stat(_) call

In practise, compat would never issue a stat call itself, but in the
future, we may remove the compat call that happens before this code
path is run.

Signed-off-by: Niels Thykier <niels@thykier.net>

1 files changed, 8 insertions, 5 deletions

diff --git a/dh_strip b/dh_strip
index edda1799..c22e4db2 100755
--- a/dh_strip
+++ b/dh_strip
@@ -191,6 +191,12 @@ sub testfile {
 	# Is it a debug library in a debug subdir?
 	return if $fn=~m/debug\/.*\.so/;
 
+	# Exploit the previous stat call to get the $mode, so we can check
+	# later if it is executable or not.
+	#
+	# NB: compat() can issue a stat, so we /should/ do this now
+	my (undef, undef, $mode, undef) = stat(_);
+
 	if (compat(10)) {
 		# In compat 10 and earlier, we used filenames and file(1)
 
@@ -206,8 +212,7 @@ sub testfile {
 			}
 		}
 
-		# Is it executable? -x isn't good enough, so we need to use stat.
-		my (undef, undef, $mode, undef) = stat(_);
+		# -x is not good enough for this test
 		if ($mode & 0111) {
 			# Ok, expensive test.
 			my $type = get_file_type($fn, 1);
@@ -220,10 +225,8 @@ sub testfile {
 		# In compat 11, we check the ELF header manually (because bulking file(1) is a pain and
 		# it is too slow otherwise)
 
-		# Exploit the previous stat call, so we can check if it is executable or not (-x is not good enough
-		# for this test)
-		my (undef, undef, $mode, undef) = stat(_);
 		if (is_so_or_exec_elf_file($fn)) {
+			# -x is not good enough for this test
 			if ($mode & 0111) {
 				push(@executables, $fn);
 			} else {