OS-5926 epoll mishandles excessive timeout negativity

Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com> Reviewed by: Ryan Zezeski <ryan.zeseski@joyent.com> Approved by: Ryan Zezeski <ryan.zeseski@joyent.com>
TritonDataCenter · Jan 31, 2017 · d21b3b2 · d21b3b2
1 parent 0e21e95
commit d21b3b2
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Showing 2 changed files with 16 additions and 6 deletions.
diff --git a/usr/src/lib/libc/port/sys/epoll.c b/usr/src/lib/libc/port/sys/epoll.c
@@ -10,7 +10,7 @@
  */
 
 /*
- * Copyright 2016 Joyent, Inc.
+ * Copyright 2017 Joyent, Inc.
  */
 
 #include <sys/types.h>
@@ -64,6 +64,15 @@
 #define	EPOLLSWIZZLED	\
 	(EPOLLRDHUP | EPOLLONESHOT | EPOLLET | EPOLLWRBAND | EPOLLWRNORM)
 
+/*
+ * The defined behavior for epoll_wait/epoll_pwait when using a timeout less
+ * than 0 is to wait for events until they arrive (or interrupted by a signal).
+ * While poll(7d) operates in this manner for a timeout of -1, using other
+ * negative values results in an immediate timeout, as if it had been set to 0.
+ * For that reason, negative values are clamped to -1.
+ */
+#define	EPOLL_TIMEOUT_CLAMP(t)	(((t) < -1) ? -1 : (t))
+
 int
 epoll_create(int size)
 {
@@ -209,7 +218,7 @@ epoll_wait(int epfd, struct epoll_event *events,
 	}
 
 	arg.dp_nfds = maxevents;
-	arg.dp_timeout = timeout;
+	arg.dp_timeout = EPOLL_TIMEOUT_CLAMP(timeout);
 	arg.dp_fds = (pollfd_t *)events;
 
 	return (ioctl(epfd, DP_POLL, &arg));
@@ -227,7 +236,7 @@ epoll_pwait(int epfd, struct epoll_event *events,
 	}
 
 	arg.dp_nfds = maxevents;
-	arg.dp_timeout = timeout;
+	arg.dp_timeout = EPOLL_TIMEOUT_CLAMP(timeout);
 	arg.dp_fds = (pollfd_t *)events;
 	arg.dp_setp = (sigset_t *)sigmask;
 

diff --git a/usr/src/uts/common/brand/lx/syscall/lx_epoll.c b/usr/src/uts/common/brand/lx/syscall/lx_epoll.c
@@ -10,7 +10,7 @@
  */
 
 /*
- * Copyright 2016 Joyent, Inc.
+ * Copyright 2017 Joyent, Inc.
  */
 
 #include <sys/types.h>
@@ -114,6 +114,7 @@ lx_epoll_create(int size)
 #define	EPOLLIGNORED 	(EPOLLMSG | EPOLLWAKEUP)
 #define	EPOLLSWIZZLED	\
 	(EPOLLRDHUP | EPOLLONESHOT | EPOLLET | EPOLLWRBAND | EPOLLWRNORM)
+#define	EPOLL_TIMEOUT_CLAMP(t)	(((t) < -1) ? -1 : (t))
 
 long
 lx_epoll_ctl(int fd, int op, int pfd, void *event)
@@ -244,7 +245,7 @@ lx_epoll_wait(int fd, void *events, int maxevents, int timeout)
 	}
 
 	arg.dp_nfds = maxevents;
-	arg.dp_timeout = timeout;
+	arg.dp_timeout = EPOLL_TIMEOUT_CLAMP(timeout);
 	arg.dp_fds = (pollfd_t *)events;
 	flag = fp->f_flag | DATAMODEL_NATIVE | FKIOCTL;
 	error = VOP_IOCTL(fp->f_vnode, DP_POLL, (uintptr_t)&arg, flag,
@@ -288,7 +289,7 @@ lx_epoll_pwait(int fd, void *events, int maxevents, int timeout, void *sigmask)
 	}
 
 	arg.dp_nfds = maxevents;
-	arg.dp_timeout = timeout;
+	arg.dp_timeout = EPOLL_TIMEOUT_CLAMP(timeout);
 	arg.dp_fds = (pollfd_t *)events;
 	flag = fp->f_flag | DATAMODEL_NATIVE | FKIOCTL;
 	error = VOP_IOCTL(fp->f_vnode, DP_PPOLL, (uintptr_t)&arg, flag,