From 85a77eea8d7114675602a33d2e067fd7c4ad0624 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>

Date: Sun, 12 Jan 2014 11:38:56 -0500

Subject: [PATCH] core: do not segfault if swap activity happens when

 /proc/swaps is not open

In https://bugzilla.redhat.com/show_bug.cgi?id=969795 systemd crashes

in swap_dispatch_reload called from manager_loop becuase m->proc_swaps

is NULL. It can legitimately be NULL if something went wrong when

initially enumerating swap devices when starting the manager. This

is probably a sign of significant trouble, but let's do our best

to recover.

---

 src/core/swap.c | 45 +++++++++++++++++++++++++++++----------------

 1 file changed, 29 insertions(+), 16 deletions(-)

diff --git a/src/core/swap.c b/src/core/swap.c

index 147f710..f295b65 100644

--- a/src/core/swap.c

+++ b/src/core/swap.c

@@ -1068,14 +1068,40 @@ static int swap_load_proc_swaps(Manager *m, bool set_flags) {

         return r;

 }

+static int open_proc_swaps(Manager *m) {

+        if (!m->proc_swaps) {

+                struct epoll_event ev = {

+                        .events = EPOLLPRI,

+                        .data.ptr = &m->swap_watch,

+                };

+

+                m->proc_swaps = fopen("/proc/swaps", "re");

+                if (!m->proc_swaps)

+                        return (errno == ENOENT) ? 0 : -errno;

+

+                m->swap_watch.type = WATCH_SWAP;

+                m->swap_watch.fd = fileno(m->proc_swaps);

+

+                if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->swap_watch.fd, &ev) < 0)

+                        return -errno;

+        }

+

+        return 0;

+}

+

 int swap_dispatch_reload(Manager *m) {

         /* This function should go as soon as the kernel properly notifies us */

+        int r;

         if (_likely_(!m->request_reload))

                 return 0;

         m->request_reload = false;

+        r = open_proc_swaps(m);

+        if (r < 0)

+                return r;

+

         return swap_fd_event(m, EPOLLPRI);

 }

@@ -1225,22 +1251,9 @@ static int swap_enumerate(Manager *m) {

         int r;

         assert(m);

-        if (!m->proc_swaps) {

-                struct epoll_event ev = {

-                        .events = EPOLLPRI,

-                        .data.ptr = &m->swap_watch,

-                };

-

-                m->proc_swaps = fopen("/proc/swaps", "re");

-                if (!m->proc_swaps)

-                        return (errno == ENOENT) ? 0 : -errno;

-

-                m->swap_watch.type = WATCH_SWAP;

-                m->swap_watch.fd = fileno(m->proc_swaps);

-

-                if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->swap_watch.fd, &ev) < 0)

-                        return -errno;

-        }

+        r = open_proc_swaps(m);

+        if (r < 0)

+                return r;

         r = swap_load_proc_swaps(m, false);

         if (r < 0)