Fix backslash escapes for -o ssh_command

sshfs.c

@@ -3984,6 +3984,7 @@ static char *tokenize_on_space(char *str)
 {
 	static char *pos = NULL;
 	char *start = NULL;
+	char *end = NULL;
 
 	if (str)
 		pos = str;
@@ -3996,22 +3997,27 @@ static char *tokenize_on_space(char *str)
 		pos++;
 
 	start = pos;
+	end = pos;
 
 	while (*pos != '\0') {
 		// break on space, but not on '\ '
-		if (*pos == ' ' && *(pos - 1) != '\\') {
-			break;
+		if (*pos == ' ') {
+			if (*(pos - 1) == '\\') {
+				end--;
+			} else {
+				break;
+			}
 		}
-		pos++;
+		*end++ = *pos++;
 	}
 
 	if (*pos == '\0') {
 		pos = NULL;
 	}
 	else {
-		*pos = '\0';
 		pos++;
 	}
+	*end = '\0';
 
 	return start;
 }

test/test_sshfs.py

@@ -1080,3 +1080,33 @@ def test_contain_symlinks_option_precedence(tmpdir, capfd) -> None:
         with pytest.raises(OSError) as exc_info:
             os.readlink(pjoin(mnt_dir, "abs"))
         assert exc_info.value.errno == errno.EPERM
+
+
+def test_backslash_escape(tmpdir, capfd):
+    """Regression test for parsing backslash escape sequences in options"""
+
+    cases = [
+        (r"one two three", "<one> <two> <three>"),
+        (r"one\\ two three", "<one two> <three>"),
+        # fuse_opt_parse interprets "\ " as " ", so these are still separate
+        (r"one two\ three", "<one> <two> <three>"),
+    ]
+
+    mnt_dir = str(tmpdir.mkdir("mnt"))
+    # we can skip cleanup since the mount always fails
+
+    for line, args in cases:
+        cmdline = base_cmdline + [
+            pjoin(basename, "sshfs"),
+            "-f",
+            "localhost:foo",
+            mnt_dir,
+            "-o",
+            "sshfs_debug",
+            "-o",
+            "ssh_command=/dev/null " + line,
+        ]
+        assert subprocess.run(cmdline).returncode != 0
+
+        captured = capfd.readouterr()
+        assert "executing </dev/null> " + args in captured.err