From 3069a93fbebce17159bf964a148c1b07221293ba Mon Sep 17 00:00:00 2001 From: Corinna Vinschen Date: Sat, 9 Jan 2016 14:53:06 +0100 Subject: [PATCH] select: Don't timeout without setting descriptor arrays to all zero * select.cc (copyfd_set): Remove. (select): Don't copy local wait fd arrays over to returned fd arrays since bits set there are not accounted for in return value. Zero out returned fd arrays instead. Always call sel.poll even in case of a timeout. Always zero out fd array when timing out. Convert while/do to do/while for clarity. Use dedicated variable as return value to decouple return value from artificial return code from sel.wait. Signed-off-by: Corinna Vinschen --- winsup/cygwin/select.cc | 35 ++++++++++++++++++++--------------- 1 file changed, 20 insertions(+), 15 deletions(-) diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc index 524e578ae..b4c37783a 100644 --- a/winsup/cygwin/select.cc +++ b/winsup/cygwin/select.cc @@ -77,8 +77,6 @@ details. */ (fd_set *) __res; \ }) -#define copyfd_set(to, from, n) memcpy (to, from, sizeof_fd_set (n)); - #define set_handle_or_return_if_not_open(h, s) \ h = (s)->fh->get_io_handle_cyg (); \ if (cygheap->fdtab.not_open ((s)->fd)) \ @@ -132,6 +130,7 @@ select (int maxfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, DWORD ms) { int res = select_stuff::select_loop; + int ret = 0; /* Record the current time for later use. */ LONGLONG start_time = gtod.msecs (); @@ -144,7 +143,7 @@ select (int maxfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, fd_set *w = allocfd_set (maxfds); fd_set *e = allocfd_set (maxfds); - while (res == select_stuff::select_loop) + do { /* Build the select record per fd linked list and set state as needed. */ @@ -187,14 +186,15 @@ select (int maxfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, select_printf ("res %d", res); if (res >= 0) { - copyfd_set (readfds, r, maxfds); - copyfd_set (writefds, w, maxfds); - copyfd_set (exceptfds, e, maxfds); - if (res == select_stuff::select_set_zero) - res = 0; - else - /* Set the bit mask from sel records */ - res = sel.poll (readfds, writefds, exceptfds) ?: select_stuff::select_loop; + UNIX_FD_ZERO (readfds, maxfds); + UNIX_FD_ZERO (writefds, maxfds); + UNIX_FD_ZERO (exceptfds, maxfds); + /* Set bit mask from sel records even in case of a timeout so we + don't miss one. This also sets ret to the right value >= 0, + matching the number of bits set in the fds records. */ + ret = sel.poll (readfds, writefds, exceptfds); + if (!ret && res != select_stuff::select_set_zero) + res = select_stuff::select_loop; } /* Always clean up everything here. If we're looping then build it all up again. */ @@ -208,7 +208,11 @@ select (int maxfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, if (now > (start_time + ms)) { select_printf ("timed out after verification"); - res = 0; + /* Set descriptor bits to zero per POSIX. */ + UNIX_FD_ZERO (readfds, maxfds); + UNIX_FD_ZERO (writefds, maxfds); + UNIX_FD_ZERO (exceptfds, maxfds); + ret = res = 0; } else { @@ -218,10 +222,11 @@ select (int maxfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, } } } + while (res == select_stuff::select_loop); - if (res < -1) - res = -1; - return res; + if (res < 0) + ret = -1; + return ret; } extern "C" int