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 #include <stdlib.h>
16 #include <errno.h>
17 #include <termio.h>
18
19 #include "tst_test.h"
20 #include "lapi/termbits.h"
21
do_test(void)22 static void do_test(void)
23 {
24 struct termios io;
25 int ptmx, pts;
26 char c = 'A';
27 int nbytes;
28
29 ptmx = SAFE_OPEN("/dev/ptmx", O_WRONLY);
30
31 if (tcgetattr(ptmx, &io) != 0)
32 tst_brk(TBROK | TERRNO, "tcgetattr() failed");
33
34 io.c_lflag = EXTPROC | ICANON;
35
36 TEST(tcsetattr(ptmx, TCSANOW, &io));
37 if (TST_RET == -1) {
38 if (TST_ERR == EINVAL)
39 tst_brk(TCONF, "tcsetattr(, , EXTPROC | ICANON) is not supported");
40 tst_brk(TBROK | TERRNO, "tcsetattr() failed");
41 }
42
43 if (unlockpt(ptmx) != 0)
44 tst_brk(TBROK | TERRNO, "unlockpt() failed");
45
46 pts = SAFE_OPEN(ptsname(ptmx), O_RDONLY);
47 /* write newline to ptmx to avoid read() on pts to block */
48 SAFE_WRITE(1, ptmx, "A\n", 2);
49 SAFE_READ(1, pts, &c, 1);
50
51 tst_res(TINFO, "Calling FIONREAD, this will hang in n_tty_ioctl() if the bug is present...");
52 SAFE_IOCTL(pts, FIONREAD, &nbytes);
53
54 SAFE_CLOSE(ptmx);
55 SAFE_CLOSE(pts);
56
57 tst_res(TPASS, "Got to the end without hanging");
58 }
59
60 static struct tst_test test = {
61 .test_all = do_test,
62 .tags = (const struct tst_tag[]) {
63 {"linux-git", "966031f34018"},
64 {}
65 }
66 };
67