1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (c) 2018 Google, Inc.
4 */
5
6 /*
7 * Regression test for commit 966031f340185 ("n_tty: fix EXTPROC vs ICANON
8 * interaction with TIOCINQ (aka FIONREAD)"). The test reproduces a hang
9 * (infinite loop in the kernel) after a pseudoterminal is put in both canonical
10 * (ICANON) and external processing (EXTPROC) mode, some data is written to the
11 * master and read from the slave, and the FIONREAD ioctl is called on the
12 * slave. This is simplified from a syzkaller-generated reproducer.
13 */
14
15 #define _GNU_SOURCE
16 #include <stdlib.h>
17 #include <errno.h>
18 #include <sys/ioctl.h>
19 #include <termios.h>
20
21 #include "tst_test.h"
22 #include "lapi/termbits.h"
23
do_test(void)24 static void do_test(void)
25 {
26 struct termios io;
27 int ptmx, pts;
28 char c = 'A';
29 int nbytes;
30
31 ptmx = SAFE_OPEN("/dev/ptmx", O_WRONLY);
32
33 if (tcgetattr(ptmx, &io) != 0)
34 tst_brk(TBROK | TERRNO, "tcgetattr() failed");
35
36 io.c_lflag = EXTPROC | ICANON;
37
38 TEST(tcsetattr(ptmx, TCSANOW, &io));
39 if (TST_RET == -1) {
40 if (TST_ERR == EINVAL)
41 tst_brk(TCONF, "tcsetattr(, , EXTPROC | ICANON) is not supported");
42 tst_brk(TBROK | TTERRNO, "tcsetattr() failed");
43 }
44
45 if (unlockpt(ptmx) != 0)
46 tst_brk(TBROK | TERRNO, "unlockpt() failed");
47
48 pts = SAFE_OPEN(ptsname(ptmx), O_RDONLY);
49 /* write newline to ptmx to avoid read() on pts to block */
50 SAFE_WRITE(1, ptmx, "A\n", 2);
51 SAFE_READ(1, pts, &c, 1);
52
53 tst_res(TINFO, "Calling FIONREAD, this will hang in n_tty_ioctl() if the bug is present...");
54 SAFE_IOCTL(pts, FIONREAD, &nbytes);
55
56 SAFE_CLOSE(ptmx);
57 SAFE_CLOSE(pts);
58
59 tst_res(TPASS, "Got to the end without hanging");
60 }
61
62 static struct tst_test test = {
63 .test_all = do_test,
64 .tags = (const struct tst_tag[]) {
65 {"linux-git", "966031f34018"},
66 {}
67 }
68 };
69