On Thu, May 20, 2010 at 04:25:54PM -0600, Eric Blake wrote:
On 05/20/2010 01:23 PM, Cole Robinson wrote:
If a directory pool contains pipes or sockets, a pool start can fail or hang:
https://bugzilla.redhat.com/show_bug.cgi?id=589577
We already try to avoid these special files, but only attempt after opening the path, which is where the problems lie. Unify volume opening into a single function which runs stat() before any open() call. Directory pools can then proceed along, ignoring the invalid files.
stat() before open() is racy. Better yet is using the O_NONBLOCK|O_NOCTTY flags of open(); gnulib guarantees they are defined, and I recently lobbied POSIX to guarantee that it will be safe on all platforms (it is already safe on Linux): http://austingroupbugs.net/view.php?id=141
+int +virStorageBackendVolOpen(const char *path) +{ + int fd; + struct stat sb; + + if (stat(path, &sb) < 0) { + virReportSystemError(errno, + _("cannot stat file '%s'"), path); + return -1; + } + + if (!S_ISREG(sb.st_mode) && + !S_ISCHR(sb.st_mode) && + !S_ISBLK(sb.st_mode)) {
Regular files and block devices I can understand, but character devices? That includes things like /dev/zero and /dev/null; do those really make sense as the backing of a volume store?
For a directory based storage pool we don't want to include block devices or character devices IMHO. Those are already dealt with via the other types of storage pool. We *do* however want to allow directories, since this allows for enumerating directories used a virtual root FS for container based virt. So this check should be !S_ISREG && S_ISDIR NB, we will of course need to make sure later code handles directories properly - ie don't have a fatal error upon trying to seek() in a directory, or even better skip that bit of code.
+ VIR_DEBUG("Skipping volume path %s, unexpected file mode.", path); + return -2; + } + + if ((fd = open(path, O_RDONLY)) < 0) { + virReportSystemError(errno, + _("cannot open volume '%s'"), + path);
In other words, I'd rather see open(path,O_RDONLY|O_NONBLOCK|O_NOCTTY) then fstat(), and not your stat()/open() sequence.
Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://deltacloud.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|