From: Dmitry V. Levin <ldv@altlinux.org>
Date: Mon, 16 May 2016 21:43:35 +0000 (+0000)
Subject: Fix decoding of epoll_ctl operation argument
X-Git-Tag: v4.12~151
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=55044d9670d46ba0f995948a226d7e45a18de5df;p=strace

Fix decoding of epoll_ctl operation argument

Consistently treat operation argument of epoll_ctl syscall as int
to match the kernel behaviour.

* epoll.c (SYS_FUNC(epoll_ctl)): Assign 2nd argument of syscall
to a variable of type unsigned int and use it in all subsequent
checks and lookups.
* tests/epoll_ctl.c (invoke_syscall): New function.
(main): Use it.
---

diff --git a/epoll.c b/epoll.c
index 20d306c4..7382e0c0 100644
--- a/epoll.c
+++ b/epoll.c
@@ -70,12 +70,13 @@ SYS_FUNC(epoll_ctl)
 {
 	printfd(tcp, tcp->u_arg[0]);
 	tprints(", ");
-	printxval(epollctls, tcp->u_arg[1], "EPOLL_CTL_???");
+	const unsigned int op = tcp->u_arg[1];
+	printxval(epollctls, op, "EPOLL_CTL_???");
 	tprints(", ");
 	printfd(tcp, tcp->u_arg[2]);
 	tprints(", ");
 	struct epoll_event ev;
-	if (EPOLL_CTL_DEL == tcp->u_arg[1])
+	if (EPOLL_CTL_DEL == op)
 		printaddr(tcp->u_arg[3]);
 	else if (!umove_or_printaddr(tcp, tcp->u_arg[3], &ev))
 		print_epoll_event(tcp, &ev, sizeof(ev), 0);
diff --git a/tests/epoll_ctl.c b/tests/epoll_ctl.c
index ffabca17..231e2710 100644
--- a/tests/epoll_ctl.c
+++ b/tests/epoll_ctl.c
@@ -8,22 +8,29 @@
 # include <sys/epoll.h>
 # include <unistd.h>
 
+static long
+invoke_syscall(unsigned long epfd, unsigned long op, unsigned long fd, void *ev)
+{
+	op |= (unsigned long) 0xffffffff00000000;
+	return syscall(__NR_epoll_ctl, epfd, op, fd, (unsigned long) ev);
+}
+
 int
 main(void)
 {
 	struct epoll_event *const ev = tail_alloc(sizeof(*ev));
 	ev->events = EPOLLIN;
 
-	long rc = syscall(__NR_epoll_ctl, -1, EPOLL_CTL_ADD, -2, ev);
+	long rc = invoke_syscall(-1U, EPOLL_CTL_ADD, -2U, ev);
 	printf("epoll_ctl(-1, EPOLL_CTL_ADD, -2, {EPOLLIN,"
 	       " {u32=%u, u64=%" PRIu64 "}}) = %ld %s (%m)\n",
 	       ev->data.u32, ev->data.u64, rc, errno2name());
 
-	rc = syscall(__NR_epoll_ctl, -3, EPOLL_CTL_DEL, -4, ev);
+	rc = invoke_syscall(-3U, EPOLL_CTL_DEL, -4U, ev);
 	printf("epoll_ctl(-3, EPOLL_CTL_DEL, -4, %p) = %ld %s (%m)\n",
 	       ev, rc, errno2name());
 
-	rc = syscall(__NR_epoll_ctl, -1L, EPOLL_CTL_MOD, -16L, 0);
+	rc = invoke_syscall(-1UL, EPOLL_CTL_MOD, -16UL, 0);
 	printf("epoll_ctl(-1, EPOLL_CTL_MOD, -16, NULL) = %ld %s (%m)\n",
 	       rc, errno2name());