>From 118c64e86641a97d44dec39e313a95b12d9bc3b2 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Date: Wed, 25 Jul 2018 00:15:18 +0900 Subject: [PATCH v2] n_tty: Protect tty->disc_data using refcount. syzbot is reporting NULL pointer dereference at n_tty_set_termios() [1]. This is because ioctl(TIOCVHANGUP) versus ioctl(TCSETS) can race. Since we don't want to introduce new locking dependency, this patch converts "struct n_tty_data *ldata = tty->disc_data;" in individual function into a function argument which follows "struct tty *", and holds tty->disc_data at each "struct tty_ldisc_ops" hook using refcount in order to ensure that memory which contains "struct n_tty_data" will not be released while processing individual function. [1] https://syzkaller.appspot.com/bug?id=1e850009fca0b64ce49dc16499bda4f7de0ab1a5 Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> --- drivers/tty/n_tty.c | 511 ++++++++++++++++++++++++++++++++-------------------- 1 file changed, 314 insertions(+), 197 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 4317422..0bb413b 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -122,6 +122,10 @@ struct n_tty_data { struct mutex atomic_read_lock; struct mutex output_lock; + + /* Race protection. */ + refcount_t users; + struct rcu_head rcu; }; #define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1)) @@ -152,10 +156,9 @@ static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i) return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)]; } -static int tty_copy_to_user(struct tty_struct *tty, void __user *to, - size_t tail, size_t n) +static int tty_copy_to_user(struct tty_struct *tty, struct n_tty_data *ldata, + void __user *to, size_t tail, size_t n) { - struct n_tty_data *ldata = tty->disc_data; size_t size = N_TTY_BUF_SIZE - tail; const void *from = read_buf_addr(ldata, tail); int uncopied; @@ -186,10 +189,8 @@ static int tty_copy_to_user(struct tty_struct *tty, void __user *to, * holds non-exclusive termios_rwsem */ -static void n_tty_kick_worker(struct tty_struct *tty) +static void n_tty_kick_worker(struct tty_struct *tty, struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; - /* Did the input worker stop? Restart it */ if (unlikely(ldata->no_room)) { ldata->no_room = 0; @@ -206,9 +207,8 @@ static void n_tty_kick_worker(struct tty_struct *tty) } } -static ssize_t chars_in_buffer(struct tty_struct *tty) +static ssize_t chars_in_buffer(struct tty_struct *tty, struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; ssize_t n = 0; if (!ldata->icanon) @@ -233,10 +233,9 @@ static void n_tty_write_wakeup(struct tty_struct *tty) kill_fasync(&tty->fasync, SIGIO, POLL_OUT); } -static void n_tty_check_throttle(struct tty_struct *tty) +static void n_tty_check_throttle(struct tty_struct *tty, + struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; - /* * Check the remaining room for the input canonicalization * mode. We don't want to throttle the driver if we're in @@ -257,12 +256,13 @@ static void n_tty_check_throttle(struct tty_struct *tty) __tty_set_flow_change(tty, 0); } -static void n_tty_check_unthrottle(struct tty_struct *tty) +static void n_tty_check_unthrottle(struct tty_struct *tty, + struct n_tty_data *ldata) { if (tty->driver->type == TTY_DRIVER_TYPE_PTY) { - if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE) + if (chars_in_buffer(tty, ldata) > TTY_THRESHOLD_UNTHROTTLE) return; - n_tty_kick_worker(tty); + n_tty_kick_worker(tty, ldata); tty_wakeup(tty->link); return; } @@ -278,9 +278,9 @@ static void n_tty_check_unthrottle(struct tty_struct *tty) while (1) { int unthrottled; tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE); - if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE) + if (chars_in_buffer(tty, ldata) > TTY_THRESHOLD_UNTHROTTLE) break; - n_tty_kick_worker(tty); + n_tty_kick_worker(tty, ldata); unthrottled = tty_unthrottle_safe(tty); if (!unthrottled) break; @@ -353,11 +353,12 @@ static void n_tty_packet_mode_flush(struct tty_struct *tty) * Locking: ctrl_lock, exclusive termios_rwsem */ -static void n_tty_flush_buffer(struct tty_struct *tty) +static void __n_tty_flush_buffer(struct tty_struct *tty, + struct n_tty_data *ldata) { down_write(&tty->termios_rwsem); - reset_buffer_flags(tty->disc_data); - n_tty_kick_worker(tty); + reset_buffer_flags(ldata); + n_tty_kick_worker(tty, ldata); if (tty->link) n_tty_packet_mode_flush(tty); @@ -413,9 +414,9 @@ static inline int is_continuation(unsigned char c, struct tty_struct *tty) * the column state and space left in the buffer */ -static int do_output_char(unsigned char c, struct tty_struct *tty, int space) +static int do_output_char(unsigned char c, struct tty_struct *tty, + struct n_tty_data *ldata, int space) { - struct n_tty_data *ldata = tty->disc_data; int spaces; if (!space) @@ -488,15 +489,15 @@ static int do_output_char(unsigned char c, struct tty_struct *tty, int space) * tty layer write lock) */ -static int process_output(unsigned char c, struct tty_struct *tty) +static int process_output(unsigned char c, struct tty_struct *tty, + struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; int space, retval; mutex_lock(&ldata->output_lock); space = tty_write_room(tty); - retval = do_output_char(c, tty, space); + retval = do_output_char(c, tty, ldata, space); mutex_unlock(&ldata->output_lock); if (retval < 0) @@ -525,9 +526,9 @@ static int process_output(unsigned char c, struct tty_struct *tty) */ static ssize_t process_output_block(struct tty_struct *tty, + struct n_tty_data *ldata, const unsigned char *buf, unsigned int nr) { - struct n_tty_data *ldata = tty->disc_data; int space; int i; const unsigned char *cp; @@ -608,9 +609,8 @@ static ssize_t process_output_block(struct tty_struct *tty, * Locking: callers must hold output_lock */ -static size_t __process_echoes(struct tty_struct *tty) +static size_t __process_echoes(struct tty_struct *tty, struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; int space, old_space; size_t tail; unsigned char c; @@ -721,7 +721,8 @@ static size_t __process_echoes(struct tty_struct *tty) break; } else { if (O_OPOST(tty)) { - int retval = do_output_char(c, tty, space); + int retval = do_output_char(c, tty, ldata, + space); if (retval < 0) break; space -= retval; @@ -754,9 +755,8 @@ static size_t __process_echoes(struct tty_struct *tty) return old_space - space; } -static void commit_echoes(struct tty_struct *tty) +static void commit_echoes(struct tty_struct *tty, struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; size_t nr, old, echoed; size_t head; @@ -776,16 +776,15 @@ static void commit_echoes(struct tty_struct *tty) } ldata->echo_commit = head; - echoed = __process_echoes(tty); + echoed = __process_echoes(tty, ldata); mutex_unlock(&ldata->output_lock); if (echoed && tty->ops->flush_chars) tty->ops->flush_chars(tty); } -static void process_echoes(struct tty_struct *tty) +static void process_echoes(struct tty_struct *tty, struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; size_t echoed; if (ldata->echo_mark == ldata->echo_tail) @@ -793,7 +792,7 @@ static void process_echoes(struct tty_struct *tty) mutex_lock(&ldata->output_lock); ldata->echo_commit = ldata->echo_mark; - echoed = __process_echoes(tty); + echoed = __process_echoes(tty, ldata); mutex_unlock(&ldata->output_lock); if (echoed && tty->ops->flush_chars) @@ -801,17 +800,15 @@ static void process_echoes(struct tty_struct *tty) } /* NB: echo_mark and echo_head should be equivalent here */ -static void flush_echoes(struct tty_struct *tty) +static void flush_echoes(struct tty_struct *tty, struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; - if ((!L_ECHO(tty) && !L_ECHONL(tty)) || ldata->echo_commit == ldata->echo_head) return; mutex_lock(&ldata->output_lock); ldata->echo_commit = ldata->echo_head; - __process_echoes(tty); + __process_echoes(tty, ldata); mutex_unlock(&ldata->output_lock); } @@ -921,10 +918,9 @@ static void echo_char_raw(unsigned char c, struct n_tty_data *ldata) * (where X is the letter representing the control char). */ -static void echo_char(unsigned char c, struct tty_struct *tty) +static void echo_char(unsigned char c, struct tty_struct *tty, + struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; - if (c == ECHO_OP_START) { add_echo_byte(ECHO_OP_START, ldata); add_echo_byte(ECHO_OP_START, ldata); @@ -961,9 +957,9 @@ static inline void finish_erasing(struct n_tty_data *ldata) * caller holds non-exclusive termios_rwsem */ -static void eraser(unsigned char c, struct tty_struct *tty) +static void eraser(unsigned char c, struct tty_struct *tty, + struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; enum { ERASE, WERASE, KILL } kill_type; size_t head; size_t cnt; @@ -985,7 +981,7 @@ static void eraser(unsigned char c, struct tty_struct *tty) if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) { ldata->read_head = ldata->canon_head; finish_erasing(ldata); - echo_char(KILL_CHAR(tty), tty); + echo_char(KILL_CHAR(tty), tty, ldata); /* Add a newline if ECHOK is on and ECHOKE is off. */ if (L_ECHOK(tty)) echo_char_raw('\n', ldata); @@ -1025,14 +1021,14 @@ static void eraser(unsigned char c, struct tty_struct *tty) ldata->erasing = 1; } /* if cnt > 1, output a multi-byte character */ - echo_char(c, tty); + echo_char(c, tty, ldata); while (--cnt > 0) { head++; echo_char_raw(read_buf(ldata, head), ldata); echo_move_back_col(ldata); } } else if (kill_type == ERASE && !L_ECHOE(tty)) { - echo_char(ERASE_CHAR(tty), tty); + echo_char(ERASE_CHAR(tty), tty, ldata); } else if (c == '\t') { unsigned int num_chars = 0; int after_tab = 0; @@ -1103,10 +1099,8 @@ static void __isig(int sig, struct tty_struct *tty) } } -static void isig(int sig, struct tty_struct *tty) +static void isig(int sig, struct tty_struct *tty, struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; - if (L_NOFLSH(tty)) { /* signal only */ __isig(sig, tty); @@ -1127,7 +1121,7 @@ static void isig(int sig, struct tty_struct *tty) tty_driver_flush_buffer(tty); /* clear input buffer */ - reset_buffer_flags(tty->disc_data); + reset_buffer_flags(ldata); /* notify pty master of flush */ if (tty->link) @@ -1151,14 +1145,13 @@ static void isig(int sig, struct tty_struct *tty) * Note: may get exclusive termios_rwsem if flushing input buffer */ -static void n_tty_receive_break(struct tty_struct *tty) +static void n_tty_receive_break(struct tty_struct *tty, + struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; - if (I_IGNBRK(tty)) return; if (I_BRKINT(tty)) { - isig(SIGINT, tty); + isig(SIGINT, tty, ldata); return; } if (I_PARMRK(tty)) { @@ -1181,10 +1174,9 @@ static void n_tty_receive_break(struct tty_struct *tty) * private. */ -static void n_tty_receive_overrun(struct tty_struct *tty) +static void n_tty_receive_overrun(struct tty_struct *tty, + struct n_tty_data *ldata) { - struct n_tty_data *ldata = tty->disc_data; - ldata->num_overrun++; if (time_after(jiffies, ldata->overrun_time + HZ) || time_after(ldata->overrun_time, jiffies)) { @@ -1205,10 +1197,10 @@ static void n_tty_receive_overrun(struct tty_struct *tty) * n_tty_receive_buf()/producer path: * caller holds non-exclusive termios_rwsem */ -static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c) +static void n_tty_receive_parity_error(struct tty_struct *tty, + struct n_tty_data *ldata, + unsigned char c) { - struct n_tty_data *ldata = tty->disc_data; - if (I_INPCK(tty)) { if (I_IGNPAR(tty)) return; @@ -1223,16 +1215,17 @@ static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c) } static void -n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c) +n_tty_receive_signal_char(struct tty_struct *tty, struct n_tty_data *ldata, + int signal, unsigned char c) { - isig(signal, tty); + isig(signal, tty, ldata); if (I_IXON(tty)) start_tty(tty); if (L_ECHO(tty)) { - echo_char(c, tty); - commit_echoes(tty); + echo_char(c, tty, ldata); + commit_echoes(tty, ldata); } else - process_echoes(tty); + process_echoes(tty, ldata); return; } @@ -1253,14 +1246,13 @@ static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c) */ static int -n_tty_receive_char_special(struct tty_struct *tty, unsigned char c) +n_tty_receive_char_special(struct tty_struct *tty, struct n_tty_data *ldata, + unsigned char c) { - struct n_tty_data *ldata = tty->disc_data; - if (I_IXON(tty)) { if (c == START_CHAR(tty)) { start_tty(tty); - process_echoes(tty); + process_echoes(tty, ldata); return 0; } if (c == STOP_CHAR(tty)) { @@ -1271,20 +1263,20 @@ static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c) if (L_ISIG(tty)) { if (c == INTR_CHAR(tty)) { - n_tty_receive_signal_char(tty, SIGINT, c); + n_tty_receive_signal_char(tty, ldata, SIGINT, c); return 0; } else if (c == QUIT_CHAR(tty)) { - n_tty_receive_signal_char(tty, SIGQUIT, c); + n_tty_receive_signal_char(tty, ldata, SIGQUIT, c); return 0; } else if (c == SUSP_CHAR(tty)) { - n_tty_receive_signal_char(tty, SIGTSTP, c); + n_tty_receive_signal_char(tty, ldata, SIGTSTP, c); return 0; } } if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) { start_tty(tty); - process_echoes(tty); + process_echoes(tty, ldata); } if (c == '\r') { @@ -1298,8 +1290,8 @@ static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c) if (ldata->icanon) { if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) || (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) { - eraser(c, tty); - commit_echoes(tty); + eraser(c, tty, ldata); + commit_echoes(tty, ldata); return 0; } if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) { @@ -1309,7 +1301,7 @@ static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c) if (L_ECHOCTL(tty)) { echo_char_raw('^', ldata); echo_char_raw('\b', ldata); - commit_echoes(tty); + commit_echoes(tty, ldata); } } return 1; @@ -1318,19 +1310,19 @@ static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c) size_t tail = ldata->canon_head; finish_erasing(ldata); - echo_char(c, tty); + echo_char(c, tty, ldata); echo_char_raw('\n', ldata); while (MASK(tail) != MASK(ldata->read_head)) { - echo_char(read_buf(ldata, tail), tty); + echo_char(read_buf(ldata, tail), tty, ldata); tail++; } - commit_echoes(tty); + commit_echoes(tty, ldata); return 0; } if (c == '\n') { if (L_ECHO(tty) || L_ECHONL(tty)) { echo_char_raw('\n', ldata); - commit_echoes(tty); + commit_echoes(tty, ldata); } goto handle_newline; } @@ -1347,8 +1339,8 @@ static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c) /* Record the column of first canon char. */ if (ldata->canon_head == ldata->read_head) echo_set_canon_col(ldata); - echo_char(c, tty); - commit_echoes(tty); + echo_char(c, tty, ldata); + commit_echoes(tty, ldata); } /* * XXX does PARMRK doubling happen for @@ -1375,9 +1367,9 @@ static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c) /* Record the column of first canon char. */ if (ldata->canon_head == ldata->read_head) echo_set_canon_col(ldata); - echo_char(c, tty); + echo_char(c, tty, ldata); } - commit_echoes(tty); + commit_echoes(tty, ldata); } /* PARMRK doubling check */ @@ -1389,21 +1381,20 @@ static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c) } static inline void -n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c) +n_tty_receive_char_inline(struct tty_struct *tty, struct n_tty_data *ldata, + unsigned char c) { - struct n_tty_data *ldata = tty->disc_data; - if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) { start_tty(tty); - process_echoes(tty); + process_echoes(tty, ldata); } if (L_ECHO(tty)) { finish_erasing(ldata); /* Record the column of first canon char. */ if (ldata->canon_head == ldata->read_head) echo_set_canon_col(ldata); - echo_char(c, tty); - commit_echoes(tty); + echo_char(c, tty, ldata); + commit_echoes(tty, ldata); } /* PARMRK doubling check */ if (c == (unsigned char) '\377' && I_PARMRK(tty)) @@ -1411,32 +1402,34 @@ static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c) put_tty_queue(c, ldata); } -static void n_tty_receive_char(struct tty_struct *tty, unsigned char c) +static void n_tty_receive_char(struct tty_struct *tty, struct n_tty_data *ldata, + unsigned char c) { - n_tty_receive_char_inline(tty, c); + n_tty_receive_char_inline(tty, ldata, c); } static inline void -n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c) +n_tty_receive_char_fast(struct tty_struct *tty, struct n_tty_data *ldata, + unsigned char c) { - struct n_tty_data *ldata = tty->disc_data; - if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) { start_tty(tty); - process_echoes(tty); + process_echoes(tty, ldata); } if (L_ECHO(tty)) { finish_erasing(ldata); /* Record the column of first canon char. */ if (ldata->canon_head == ldata->read_head) echo_set_canon_col(ldata); - echo_char(c, tty); - commit_echoes(tty); + echo_char(c, tty, ldata); + commit_echoes(tty, ldata); } put_tty_queue(c, ldata); } -static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c) +static void n_tty_receive_char_closing(struct tty_struct *tty, + struct n_tty_data *ldata, + unsigned char c) { if (I_ISTRIP(tty)) c &= 0x7f; @@ -1451,24 +1444,25 @@ static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c) c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty))) { start_tty(tty); - process_echoes(tty); + process_echoes(tty, ldata); } } } static void -n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag) +n_tty_receive_char_flagged(struct tty_struct *tty, struct n_tty_data *ldata, + unsigned char c, char flag) { switch (flag) { case TTY_BREAK: - n_tty_receive_break(tty); + n_tty_receive_break(tty, ldata); break; case TTY_PARITY: case TTY_FRAME: - n_tty_receive_parity_error(tty, c); + n_tty_receive_parity_error(tty, ldata, c); break; case TTY_OVERRUN: - n_tty_receive_overrun(tty); + n_tty_receive_overrun(tty, ldata); break; default: tty_err(tty, "unknown flag %d\n", flag); @@ -1477,26 +1471,24 @@ static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c) } static void -n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag) +n_tty_receive_char_lnext(struct tty_struct *tty, struct n_tty_data *ldata, + unsigned char c, char flag) { - struct n_tty_data *ldata = tty->disc_data; - ldata->lnext = 0; if (likely(flag == TTY_NORMAL)) { if (I_ISTRIP(tty)) c &= 0x7f; if (I_IUCLC(tty) && L_IEXTEN(tty)) c = tolower(c); - n_tty_receive_char(tty, c); + n_tty_receive_char(tty, ldata, c); } else - n_tty_receive_char_flagged(tty, c, flag); + n_tty_receive_char_flagged(tty, ldata, c, flag); } static void -n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp, - char *fp, int count) +n_tty_receive_buf_real_raw(struct tty_struct *tty, struct n_tty_data *ldata, + const unsigned char *cp, char *fp, int count) { - struct n_tty_data *ldata = tty->disc_data; size_t n, head; head = ldata->read_head & (N_TTY_BUF_SIZE - 1); @@ -1513,10 +1505,9 @@ static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c) } static void -n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp, - char *fp, int count) +n_tty_receive_buf_raw(struct tty_struct *tty, struct n_tty_data *ldata, + const unsigned char *cp, char *fp, int count) { - struct n_tty_data *ldata = tty->disc_data; char flag = TTY_NORMAL; while (count--) { @@ -1525,13 +1516,13 @@ static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c) if (likely(flag == TTY_NORMAL)) put_tty_queue(*cp++, ldata); else - n_tty_receive_char_flagged(tty, *cp++, flag); + n_tty_receive_char_flagged(tty, ldata, *cp++, flag); } } static void -n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp, - char *fp, int count) +n_tty_receive_buf_closing(struct tty_struct *tty, struct n_tty_data *ldata, + const unsigned char *cp, char *fp, int count) { char flag = TTY_NORMAL; @@ -1539,15 +1530,14 @@ static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c) if (fp) flag = *fp++; if (likely(flag == TTY_NORMAL)) - n_tty_receive_char_closing(tty, *cp++); + n_tty_receive_char_closing(tty, ldata, *cp++); } } static void -n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp, - char *fp, int count) +n_tty_receive_buf_standard(struct tty_struct *tty, struct n_tty_data *ldata, + const unsigned char *cp, char *fp, int count) { - struct n_tty_data *ldata = tty->disc_data; char flag = TTY_NORMAL; while (count--) { @@ -1565,23 +1555,24 @@ static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c) continue; } if (!test_bit(c, ldata->char_map)) - n_tty_receive_char_inline(tty, c); - else if (n_tty_receive_char_special(tty, c) && count) { + n_tty_receive_char_inline(tty, ldata, c); + else if (n_tty_receive_char_special(tty, ldata, c) && + count) { if (fp) flag = *fp++; - n_tty_receive_char_lnext(tty, *cp++, flag); + n_tty_receive_char_lnext(tty, ldata, *cp++, + flag); count--; } } else - n_tty_receive_char_flagged(tty, *cp++, flag); + n_tty_receive_char_flagged(tty, ldata, *cp++, flag); } } static void -n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp, - char *fp, int count) +n_tty_receive_buf_fast(struct tty_struct *tty, struct n_tty_data *ldata, + const unsigned char *cp, char *fp, int count) { - struct n_tty_data *ldata = tty->disc_data; char flag = TTY_NORMAL; while (count--) { @@ -1591,46 +1582,47 @@ static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c) unsigned char c = *cp++; if (!test_bit(c, ldata->char_map)) - n_tty_receive_char_fast(tty, c); - else if (n_tty_receive_char_special(tty, c) && count) { + n_tty_receive_char_fast(tty, ldata, c); + else if (n_tty_receive_char_special(tty, ldata, c) && + count) { if (fp) flag = *fp++; - n_tty_receive_char_lnext(tty, *cp++, flag); + n_tty_receive_char_lnext(tty, ldata, *cp++, + flag); count--; } } else - n_tty_receive_char_flagged(tty, *cp++, flag); + n_tty_receive_char_flagged(tty, ldata, *cp++, flag); } } -static void __receive_buf(struct tty_struct *tty, const unsigned char *cp, - char *fp, int count) +static void __receive_buf(struct tty_struct *tty, struct n_tty_data *ldata, + const unsigned char *cp, char *fp, int count) { - struct n_tty_data *ldata = tty->disc_data; bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty)); if (ldata->real_raw) - n_tty_receive_buf_real_raw(tty, cp, fp, count); + n_tty_receive_buf_real_raw(tty, ldata, cp, fp, count); else if (ldata->raw || (L_EXTPROC(tty) && !preops)) - n_tty_receive_buf_raw(tty, cp, fp, count); + n_tty_receive_buf_raw(tty, ldata, cp, fp, count); else if (tty->closing && !L_EXTPROC(tty)) - n_tty_receive_buf_closing(tty, cp, fp, count); + n_tty_receive_buf_closing(tty, ldata, cp, fp, count); else { if (ldata->lnext) { char flag = TTY_NORMAL; if (fp) flag = *fp++; - n_tty_receive_char_lnext(tty, *cp++, flag); + n_tty_receive_char_lnext(tty, ldata, *cp++, flag); count--; } if (!preops && !I_PARMRK(tty)) - n_tty_receive_buf_fast(tty, cp, fp, count); + n_tty_receive_buf_fast(tty, ldata, cp, fp, count); else - n_tty_receive_buf_standard(tty, cp, fp, count); + n_tty_receive_buf_standard(tty, ldata, cp, fp, count); - flush_echoes(tty); + flush_echoes(tty, ldata); if (tty->ops->flush_chars) tty->ops->flush_chars(tty); } @@ -1681,10 +1673,9 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp, * publishes commit_head or canon_head */ static int -n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp, - char *fp, int count, int flow) +n_tty_receive_buf_common(struct tty_struct *tty, struct n_tty_data *ldata, + const unsigned char *cp, char *fp, int count, int flow) { - struct n_tty_data *ldata = tty->disc_data; int room, n, rcvd = 0, overflow; down_read(&tty->termios_rwsem); @@ -1724,7 +1715,7 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp, /* ignore parity errors if handling overflow */ if (!overflow || !fp || *fp != TTY_PARITY) - __receive_buf(tty, cp, fp, n); + __receive_buf(tty, ldata, cp, fp, n); cp += n; if (fp) @@ -1743,23 +1734,25 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp, __tty_set_flow_change(tty, 0); } } else - n_tty_check_throttle(tty); + n_tty_check_throttle(tty, ldata); up_read(&tty->termios_rwsem); return rcvd; } -static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp, - char *fp, int count) +static void __n_tty_receive_buf(struct tty_struct *tty, + struct n_tty_data *ldata, + const unsigned char *cp, char *fp, int count) { - n_tty_receive_buf_common(tty, cp, fp, count, 0); + n_tty_receive_buf_common(tty, ldata, cp, fp, count, 0); } -static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp, - char *fp, int count) +static int __n_tty_receive_buf2(struct tty_struct *tty, + struct n_tty_data *ldata, + const unsigned char *cp, char *fp, int count) { - return n_tty_receive_buf_common(tty, cp, fp, count, 1); + return n_tty_receive_buf_common(tty, ldata, cp, fp, count, 1); } /** @@ -1776,10 +1769,9 @@ static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp, * Locking: Caller holds tty->termios_rwsem */ -static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old) +static void __n_tty_set_termios(struct tty_struct *tty, + struct n_tty_data *ldata, struct ktermios *old) { - struct n_tty_data *ldata = tty->disc_data; - if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) { bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE); ldata->line_start = ldata->read_tail; @@ -1852,7 +1844,7 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old) */ if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) { start_tty(tty); - process_echoes(tty); + process_echoes(tty, ldata); } /* The termios change make the tty ready for I/O */ @@ -1869,16 +1861,20 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old) * discipline change. The function will not be called while other * ldisc methods are in progress. */ - +static void put_n_tty(struct n_tty_data *ldata); static void n_tty_close(struct tty_struct *tty) { - struct n_tty_data *ldata = tty->disc_data; + struct n_tty_data *ldata = xchg(&tty->disc_data, NULL); if (tty->link) n_tty_packet_mode_flush(tty); - vfree(ldata); - tty->disc_data = NULL; + /* + * The xchg() above and this NULL test are rather paranoid checks. + * Caller should not call close() twice. + */ + if (ldata) + put_n_tty(ldata); } /** @@ -1890,7 +1886,7 @@ static void n_tty_close(struct tty_struct *tty) * other events will occur in parallel. No further open will occur * until a close. */ - +static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old); static int n_tty_open(struct tty_struct *tty) { struct n_tty_data *ldata; @@ -1900,6 +1896,7 @@ static int n_tty_open(struct tty_struct *tty) if (!ldata) return -ENOMEM; + refcount_set(&ldata->users, 1); ldata->overrun_time = jiffies; mutex_init(&ldata->atomic_read_lock); mutex_init(&ldata->output_lock); @@ -1913,9 +1910,9 @@ static int n_tty_open(struct tty_struct *tty) return 0; } -static inline int input_available_p(struct tty_struct *tty, int poll) +static inline int input_available_p(struct tty_struct *tty, + struct n_tty_data *ldata, int poll) { - struct n_tty_data *ldata = tty->disc_data; int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1; if (ldata->icanon && !L_EXTPROC(tty)) @@ -1944,12 +1941,10 @@ static inline int input_available_p(struct tty_struct *tty, int poll) * read_tail published */ -static int copy_from_read_buf(struct tty_struct *tty, - unsigned char __user **b, - size_t *nr) +static int copy_from_read_buf(struct tty_struct *tty, struct n_tty_data *ldata, + unsigned char __user **b, size_t *nr) { - struct n_tty_data *ldata = tty->disc_data; int retval; size_t n; bool is_eof; @@ -2000,10 +1995,9 @@ static int copy_from_read_buf(struct tty_struct *tty, */ static int canon_copy_from_read_buf(struct tty_struct *tty, - unsigned char __user **b, - size_t *nr) + struct n_tty_data *ldata, + unsigned char __user **b, size_t *nr) { - struct n_tty_data *ldata = tty->disc_data; size_t n, size, more, c; size_t eol; size_t tail; @@ -2043,7 +2037,7 @@ static int canon_copy_from_read_buf(struct tty_struct *tty, n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n", __func__, eol, found, n, c, tail, more); - ret = tty_copy_to_user(tty, *b, tail, n); + ret = tty_copy_to_user(tty, ldata, *b, tail, n); if (ret) return -EFAULT; *b += n; @@ -2113,10 +2107,10 @@ static int job_control(struct tty_struct *tty, struct file *file) * publishes read_tail */ -static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, - unsigned char __user *buf, size_t nr) +static ssize_t __n_tty_read(struct tty_struct *tty, struct n_tty_data *ldata, + struct file *file, unsigned char __user *buf, + size_t nr) { - struct n_tty_data *ldata = tty->disc_data; unsigned char __user *b = buf; DEFINE_WAIT_FUNC(wait, woken_wake_function); int c; @@ -2178,11 +2172,11 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, break; } - if (!input_available_p(tty, 0)) { + if (!input_available_p(tty, ldata, 0)) { up_read(&tty->termios_rwsem); tty_buffer_flush_work(tty->port); down_read(&tty->termios_rwsem); - if (!input_available_p(tty, 0)) { + if (!input_available_p(tty, ldata, 0)) { if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) { retval = -EIO; break; @@ -2216,7 +2210,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, } if (ldata->icanon && !L_EXTPROC(tty)) { - retval = canon_copy_from_read_buf(tty, &b, &nr); + retval = canon_copy_from_read_buf(tty, ldata, &b, &nr); if (retval) break; } else { @@ -2232,15 +2226,15 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, nr--; } - uncopied = copy_from_read_buf(tty, &b, &nr); - uncopied += copy_from_read_buf(tty, &b, &nr); + uncopied = copy_from_read_buf(tty, ldata, &b, &nr); + uncopied += copy_from_read_buf(tty, ldata, &b, &nr); if (uncopied) { retval = -EFAULT; break; } } - n_tty_check_unthrottle(tty); + n_tty_check_unthrottle(tty, ldata); if (b - buf >= minimum) break; @@ -2248,7 +2242,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, timeout = time; } if (tail != ldata->read_tail) - n_tty_kick_worker(tty); + n_tty_kick_worker(tty, ldata); up_read(&tty->termios_rwsem); remove_wait_queue(&tty->read_wait, &wait); @@ -2282,8 +2276,9 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, * lock themselves) */ -static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, - const unsigned char *buf, size_t nr) +static ssize_t __n_tty_write(struct tty_struct *tty, struct n_tty_data *ldata, + struct file *file, const unsigned char *buf, + size_t nr) { const unsigned char *b = buf; DEFINE_WAIT_FUNC(wait, woken_wake_function); @@ -2300,7 +2295,7 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, down_read(&tty->termios_rwsem); /* Write out any echoed characters that are still pending */ - process_echoes(tty); + process_echoes(tty, ldata); add_wait_queue(&tty->write_wait, &wait); while (1) { @@ -2314,7 +2309,8 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, } if (O_OPOST(tty)) { while (nr > 0) { - ssize_t num = process_output_block(tty, b, nr); + ssize_t num = process_output_block(tty, ldata, + b, nr); if (num < 0) { if (num == -EAGAIN) break; @@ -2326,15 +2322,13 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, if (nr == 0) break; c = *b; - if (process_output(c, tty) < 0) + if (process_output(c, tty, ldata) < 0) break; b++; nr--; } if (tty->ops->flush_chars) tty->ops->flush_chars(tty); } else { - struct n_tty_data *ldata = tty->disc_data; - while (nr > 0) { mutex_lock(&ldata->output_lock); c = tty->ops->write(tty, b, nr); @@ -2383,18 +2377,18 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, * Called without the kernel lock held - fine */ -static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file, - poll_table *wait) +static __poll_t __n_tty_poll(struct tty_struct *tty, struct n_tty_data *ldata, + struct file *file, poll_table *wait) { __poll_t mask = 0; poll_wait(file, &tty->read_wait, wait); poll_wait(file, &tty->write_wait, wait); - if (input_available_p(tty, 1)) + if (input_available_p(tty, ldata, 1)) mask |= EPOLLIN | EPOLLRDNORM; else { tty_buffer_flush_work(tty->port); - if (input_available_p(tty, 1)) + if (input_available_p(tty, ldata, 1)) mask |= EPOLLIN | EPOLLRDNORM; } if (tty->packet && tty->link->ctrl_status) @@ -2429,10 +2423,9 @@ static unsigned long inq_canon(struct n_tty_data *ldata) return nr; } -static int n_tty_ioctl(struct tty_struct *tty, struct file *file, - unsigned int cmd, unsigned long arg) +static int __n_tty_ioctl(struct tty_struct *tty, struct n_tty_data *ldata, + struct file *file, unsigned int cmd, unsigned long arg) { - struct n_tty_data *ldata = tty->disc_data; int retval; switch (cmd) { @@ -2451,6 +2444,130 @@ static int n_tty_ioctl(struct tty_struct *tty, struct file *file, } } +static struct n_tty_data *tryget_n_tty(struct tty_struct *tty) +{ + struct n_tty_data *ldata; + bool ret; + + rcu_read_lock(); + ldata = tty->disc_data; + ret = ldata && refcount_inc_not_zero(&ldata->users); + rcu_read_unlock(); + if (ret) + return ldata; + return NULL; +} + +static void free_n_tty(struct rcu_head *head) +{ + struct n_tty_data *ldata = container_of(head, struct n_tty_data, rcu); + + vfree(ldata); +} + +static void put_n_tty(struct n_tty_data *ldata) +{ + if (refcount_dec_and_test(&ldata->users)) + call_rcu(&ldata->rcu, free_n_tty); +} + +static void n_tty_flush_buffer(struct tty_struct *tty) +{ + struct n_tty_data *ldata = tryget_n_tty(tty); + + if (!ldata) + return; + __n_tty_flush_buffer(tty, ldata); + put_n_tty(ldata); +} + +static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, + unsigned char __user *buf, size_t nr) +{ + struct n_tty_data *ldata = tryget_n_tty(tty); + ssize_t retval; + + if (!ldata) + return -EIO; + retval = __n_tty_read(tty, ldata, file, buf, nr); + put_n_tty(ldata); + return retval; +} + +static ssize_t n_tty_write(struct tty_struct *tty, struct file *file, + const unsigned char *buf, size_t nr) +{ + struct n_tty_data *ldata = tryget_n_tty(tty); + ssize_t retval; + + if (!ldata) + return -EIO; + retval = __n_tty_write(tty, ldata, file, buf, nr); + put_n_tty(ldata); + return retval; +} + +static int n_tty_ioctl(struct tty_struct *tty, struct file *file, + unsigned int cmd, unsigned long arg) +{ + struct n_tty_data *ldata = tryget_n_tty(tty); + int retval; + + if (!ldata) + return -EIO; + retval = __n_tty_ioctl(tty, ldata, file, cmd, arg); + put_n_tty(ldata); + return retval; +} + +static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old) +{ + struct n_tty_data *ldata = tryget_n_tty(tty); + + if (!ldata) + return; + __n_tty_set_termios(tty, ldata, old); + put_n_tty(ldata); +} + +static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file, + poll_table *wait) +{ + struct n_tty_data *ldata = tryget_n_tty(tty); + __poll_t retval; + + if (!ldata) + return POLLERR|POLLHUP; + retval = __n_tty_poll(tty, ldata, file, wait); + put_n_tty(ldata); + return retval; + +} + +static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp, + char *fp, int count) +{ + struct n_tty_data *ldata = tryget_n_tty(tty); + + if (!ldata) + return; + __n_tty_receive_buf(tty, ldata, cp, fp, count); + put_n_tty(ldata); +} + +static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp, + char *fp, int count) +{ + struct n_tty_data *ldata = tryget_n_tty(tty); + int retval; + + if (!ldata) + return -EIO; + retval = __n_tty_receive_buf2(tty, ldata, cp, fp, count); + put_n_tty(ldata); + return retval; +} + static struct tty_ldisc_ops n_tty_ops = { .magic = TTY_LDISC_MAGIC, .name = "n_tty", -- 1.8.3.1
