[openssh-commits] [openssh] 01/01: fix edge case in poll(2) wrapper

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commit a1d42a6ce0398da3833bedf374ef2571af7fea50
Author: Damien Miller <djm at mindrot.org>
Date:   Fri Jan 14 13:49:32 2022 +1100

    fix edge case in poll(2) wrapper
    
    Correct handling of select(2) exceptfds. These should only be consulted
    for POLLPRI flagged pfds and not unconditionally converted to POLLERR.
    
    with and ok dtucker@
---
 openbsd-compat/bsd-poll.c | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/openbsd-compat/bsd-poll.c b/openbsd-compat/bsd-poll.c
index 8084776c..f8b427fc 100644
--- a/openbsd-compat/bsd-poll.c
+++ b/openbsd-compat/bsd-poll.c
@@ -33,8 +33,8 @@
 /*
  * A minimal implementation of ppoll(2), built on top of pselect(2).
  *
- * Only supports POLLIN and POLLOUT flags in pfd.events, and POLLIN, POLLOUT
- * and POLLERR flags in revents.
+ * Only supports POLLIN, POLLOUT and POLLPRI flags in pfd.events and
+ * revents. Notably POLLERR, POLLHUP and POLLNVAL are not supported.
  *
  * Supports pfd.fd = -1 meaning "unused" although it's not standard.
  */
@@ -71,14 +71,12 @@ ppoll(struct pollfd *fds, nfds_t nfds, const struct timespec *tmoutp,
 		fd = fds[i].fd;
 		if (fd == -1)
 			continue;
-		if (fds[i].events & POLLIN) {
+		if (fds[i].events & POLLIN)
 			FD_SET(fd, readfds);
-			FD_SET(fd, exceptfds);
-		}
-		if (fds[i].events & POLLOUT) {
+		if (fds[i].events & POLLOUT)
 			FD_SET(fd, writefds);
+		if (fds[i].events & POLLPRI)
 			FD_SET(fd, exceptfds);
-		}
 	}
 
 	ret = pselect(maxfd + 1, readfds, writefds, exceptfds, tmoutp, sigmask);
@@ -90,15 +88,12 @@ ppoll(struct pollfd *fds, nfds_t nfds, const struct timespec *tmoutp,
 		fds[i].revents = 0;
 		if (fd == -1)
 			continue;
-		if (FD_ISSET(fd, readfds)) {
+		if (FD_ISSET(fd, readfds))
 			fds[i].revents |= POLLIN;
-		}
-		if (FD_ISSET(fd, writefds)) {
+		if (FD_ISSET(fd, writefds))
 			fds[i].revents |= POLLOUT;
-		}
-		if (FD_ISSET(fd, exceptfds)) {
-			fds[i].revents |= POLLERR;
-		}
+		if (FD_ISSET(fd, exceptfds))
+			fds[i].revents |= POLLPRI;
 	}
 
 out:

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