n_tty: Remove overflow tests from receive_buf() path

Always pre-figure the space available in the read_buf and limit
the inbound receive request to that amount.

For compatibility reasons with the non-flow-controlled interface,
n_tty_receive_buf() will continue filling read_buf until all data
has been received or receive_room() returns 0.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 37 insertions, 48 deletions

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index adc06af3a075..f66d95f949d1 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -316,12 +316,9 @@ static inline void n_tty_check_unthrottle(struct tty_struct *tty)
  *      not active.
  */
 
-static void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
+static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
 {
-        if (read_cnt(ldata) < N_TTY_BUF_SIZE) {
-                *read_buf_addr(ldata, ldata->read_head) = c;
-                ldata->read_head++;
-        }
+        *read_buf_addr(ldata, ldata->read_head++) = c;
 }
 
 /**
@@ -1333,11 +1330,6 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
                         return;
                 }
                 if (c == '\n') {
-                        if (read_cnt(ldata) >= N_TTY_BUF_SIZE) {
-                                if (L_ECHO(tty))
-                                        process_output('\a', tty);
-                                return;
-                        }
                         if (L_ECHO(tty) || L_ECHONL(tty)) {
                                 echo_char_raw('\n', ldata);
                                 commit_echoes(tty);
@@ -1345,8 +1337,6 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
                         goto handle_newline;
                 }
                 if (c == EOF_CHAR(tty)) {
-                        if (read_cnt(ldata) >= N_TTY_BUF_SIZE)
-                                return;
                         c = __DISABLED_CHAR;
                         goto handle_newline;
                 }
@@ -1354,11 +1344,6 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
                     (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
                         parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
                                  ? 1 : 0;
-                        if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk)) {
-                                if (L_ECHO(tty))
-                                        process_output('\a', tty);
-                                return;
-                        }
                         /*
                          * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
                          */
@@ -1388,12 +1373,6 @@ handle_newline:
         }
 
         parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
-        if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
-                /* beep if no space */
-                if (L_ECHO(tty))
-                        process_output('\a', tty);
-                return;
-        }
         if (L_ECHO(tty)) {
                 finish_erasing(ldata);
                 if (c == '\n')
@@ -1432,14 +1411,6 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
                         start_tty(tty);
                         process_echoes(tty);
                 }
-
-                parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
-                if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
-                        /* beep if no space */
-                        if (L_ECHO(tty))
-                                process_output('\a', tty);
-                        return;
-                }
                 if (L_ECHO(tty)) {
                         finish_erasing(ldata);
                         /* Record the column of first canon char. */
@@ -1448,6 +1419,7 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
                         echo_char(c, tty);
                         commit_echoes(tty);
                 }
+                parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
                 if (parmrk)
                         put_tty_queue(c, ldata);
                 put_tty_queue(c, ldata);
@@ -1476,13 +1448,6 @@ n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
                         start_tty(tty);
                         process_echoes(tty);
                 }
-
-                if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - 1)) {
-                        /* beep if no space */
-                        if (L_ECHO(tty))
-                                process_output('\a', tty);
-                        return;
-                }
                 if (L_ECHO(tty)) {
                         finish_erasing(ldata);
                         /* Record the column of first canon char. */
@@ -1691,8 +1656,23 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
                               char *fp, int count)
 {
+        int room, n;
+
         down_read(&tty->termios_rwsem);
-        __receive_buf(tty, cp, fp, count);
+
+        while (1) {
+                room = receive_room(tty);
+                n = min(count, room);
+                if (!n)
+                        break;
+                __receive_buf(tty, cp, fp, n);
+                cp += n;
+                if (fp)
+                        fp += n;
+                count -= n;
+        }
+
+        tty->receive_room = room;
         n_tty_check_throttle(tty);
         up_read(&tty->termios_rwsem);
 }
@@ -1701,22 +1681,31 @@ static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
                               char *fp, int count)
 {
         struct n_tty_data *ldata = tty->disc_data;
-        int room;
+        int room, n, rcvd = 0;
 
         down_read(&tty->termios_rwsem);
 
-        tty->receive_room = room = receive_room(tty);
-        if (!room)
-                ldata->no_room = 1;
-        count = min(count, room);
-        if (count) {
-                __receive_buf(tty, cp, fp, count);
-                n_tty_check_throttle(tty);
+        while (1) {
+                room = receive_room(tty);
+                n = min(count, room);
+                if (!n) {
+                        if (!room)
+                                ldata->no_room = 1;
+                        break;
+                }
+                __receive_buf(tty, cp, fp, n);
+                cp += n;
+                if (fp)
+                        fp += n;
+                count -= n;
+                rcvd += n;
         }
 
+        tty->receive_room = room;
+        n_tty_check_throttle(tty);
         up_read(&tty->termios_rwsem);
 
-        return count;
+        return rcvd;
 }
 
 int is_ignored(int sig)