From 8d74c49c208f4e36ef844a584557fc5577272c27 Mon Sep 17 00:00:00 2001 From: David Herrmann Date: Fri, 30 Aug 2013 15:50:41 +0200 Subject: [PATCH] libudev: enumerate: fix NULL-deref for subsystem-matches udev_device_get_subsystem() may return NULL if no subsystem could be figured out by libudev. This might be due to OOM or if the device disconnected between the udev_device_new() call and udev_device_get_subsystem(). Therefore, we need to handle subsystem==NULL safely. Instead of testing for it in each helper, we treat subsystem==NULL as empty subsystem in match_subsystem(). Backtrace of udev_enumerate with an input-device disconnecting in exactly this time-frame: (gdb) bt #0 0x00007ffff569dc24 in strnlen () from /usr/lib/libc.so.6 #1 0x00007ffff56d9e04 in fnmatch@@GLIBC_2.2.5 () from /usr/lib/libc.so.6 #2 0x00007ffff5beb83d in match_subsystem (udev_enumerate=0x7a05f0, subsystem=0x0) at src/libudev/libudev-enumerate.c:727 #3 0x00007ffff5bebb30 in parent_add_child (enumerate=enumerate@entry=0x7a05f0, path=) at src/libudev/libudev-enumerate.c:834 #4 0x00007ffff5bebc3f in parent_crawl_children (enumerate=enumerate@entry=0x7a05f0, path=0x7a56b0 "/sys/devices//input/input97", maxdepth=maxdepth@entry=254) at src/libudev/libudev-enumerate.c:866 #5 0x00007ffff5bebc54 in parent_crawl_children (enumerate=enumerate@entry=0x7a05f0, path=0x79e8c0 "/sys/devices//input", maxdepth=maxdepth@entry=255) at src/libudev/libudev-enumerate.c:868 #6 0x00007ffff5bebc54 in parent_crawl_children (enumerate=enumerate@entry=0x7a05f0, path=path@entry=0x753190 "/sys/devices/", maxdepth=maxdepth@entry=256) at src/libudev/libudev-enumerate.c:868 #7 0x00007ffff5bec7df in scan_devices_children (enumerate=0x7a05f0) at src/libudev/libudev-enumerate.c:882 #8 udev_enumerate_scan_devices (udev_enumerate=udev_enumerate@entry=0x7a05f0) at src/libudev/libudev-enumerate.c:919 #9 0x00007ffff5df8777 in () at some/file.c:181 --- src/libudev/libudev-enumerate.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/src/libudev/libudev-enumerate.c b/src/libudev/libudev-enumerate.c index b96e5b2..385829d 100644 --- a/src/libudev/libudev-enumerate.c +++ b/src/libudev/libudev-enumerate.c @@ -721,6 +721,8 @@ static bool match_subsystem(struct udev_enumerate *udev_enumerate, const char *s { struct udev_list_entry *list_entry; + subsystem = subsystem ? : ""; + udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_enumerate->subsystem_nomatch_list)) { if (fnmatch(udev_list_entry_get_name(list_entry), subsystem, 0) == 0) return false;