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telnetd: fix bad interaction with vhangup() from login

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2019-01-06 19:06:01 +01:00
parent 935afafcf3
commit 39b18196f8
1 changed files with 16 additions and 2 deletions
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18
networking/telnetd.c
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@ -865,11 +865,25 @@ int telnetd_main(int argc UNUSED_PARAM, char **argv)
skip3:
if (/*ts->size2 < BUFSIZE &&*/ FD_ISSET(ts->ptyfd, &rdfdset)) {
/* Read from pty to buffer 2 */
int eio = 0;
read_pty:
count = MIN(BUFSIZE - ts->rdidx2, BUFSIZE - ts->size2);
count = safe_read(ts->ptyfd, TS_BUF2(ts) + ts->rdidx2, count);
if (count <= 0) {
if (count < 0 && errno == EAGAIN)
goto skip4;
if (count < 0) {
if (errno == EAGAIN)
goto skip4;
/* login process might call vhangup(),
* which causes intermittent EIOs on read above
* (observed on kernel 4.12.0). Try up to 10 ms.
*/
if (errno == EIO && eio < 10) {
eio++;
//bb_error_msg("EIO pty %u", eio);
usleep(1000);
goto read_pty;
}
}
goto kill_session;
}
ts->size2 += count;