On Thu, May 28, 2015 at 10:03:28AM -0500, Eric W. Biederman wrote: > Serge Hallyn <[email protected]> writes: > > > Quoting Andy Lutomirski ([email protected]): > >> On Fri, May 22, 2015 at 10:39 AM, Eric W. Biederman > >> <[email protected]> wrote: > >> > I had hoped to get some Tested-By's on that patch series. > >> > >> Sorry, I've been totally swamped. > >> > >> I suspect that Sandstorm is okay, but I haven't had a chance to test > >> it for real. Sandstorm makes only limited use of proc and sysfs in > >> containers, but I'll see if I can test it for real this weekend. > > > > Testing this with unprivileged containers, I get > > > > lxc-start: conf.c: lxc_mount_auto_mounts: 808 Operation not permitted > > - error mounting sysfs on > > /usr/lib/x86_64-linux-gnu/lxc/sys/devices/virtual/net flags 0 > > Grr.. I was afraid this would break something. :( > > Looking at my system I see that sysfs is currently mounted > "nosuid,nodev,noexec" > > Looking at the lxc-start code I don't see it as including any of those > mount options. In practice for sysfs I think those options are > meaningless (as there should be no devices and nothing executable in > sysfs) but I can understand the past concerns with chmod on virtual > filesystems that would incline people to use them, so I think the > failure is reporting a legitimate security issue in the lxc userspace > code where the the unprivileged code is currently attempting to give > greater access to sysfs than was given by the original mount of sysfs. > > As nosuid,nodev,noexec should not impair the operation of sysfs > operation it looks like you can always specify those options and just > make this concern go away. > > Something like the untested patch below I expect. > > diff --git a/src/lxc/conf.c b/src/lxc/conf.c > index 9870455b3cae..d9ccd03afe68 100644 > --- a/src/lxc/conf.c > +++ b/src/lxc/conf.c > @@ -770,8 +770,8 @@ static int lxc_mount_auto_mounts(struct lxc_conf *conf, > int flags, struct lxc_ha > { LXC_AUTO_PROC_MASK, LXC_AUTO_PROC_MIXED, > "%r/proc/sysrq-trigger", "%r/proc/sysrq-trigger", > NULL, MS_BIND, NULL }, > { LXC_AUTO_PROC_MASK, LXC_AUTO_PROC_MIXED, NULL, > "%r/proc/sysrq-trigger", NULL, > MS_REMOUNT|MS_BIND|MS_RDONLY, NULL }, > { LXC_AUTO_PROC_MASK, LXC_AUTO_PROC_RW, "proc", > "%r/proc", "proc", > MS_NODEV|MS_NOEXEC|MS_NOSUID, NULL }, > - { LXC_AUTO_SYS_MASK, LXC_AUTO_SYS_RW, "sysfs", > "%r/sys", "sysfs", > 0, NULL }, > - { LXC_AUTO_SYS_MASK, LXC_AUTO_SYS_RO, "sysfs", > "%r/sys", "sysfs", > MS_RDONLY, NULL }, > + { LXC_AUTO_SYS_MASK, LXC_AUTO_SYS_RW, "sysfs", > "%r/sys", "sysfs", > MS_NODEV|MS_NOEXEC|MS_NOSUID, NULL }, > + { LXC_AUTO_SYS_MASK, LXC_AUTO_SYS_RO, "sysfs", > "%r/sys", "sysfs", > MS_NODEV|MS_NOEXEC|MS_NOSUID|MS_RDONLY, NULL }, > { LXC_AUTO_SYS_MASK, LXC_AUTO_SYS_MIXED, "sysfs", > "%r/sys", "sysfs", > MS_NODEV|MS_NOEXEC|MS_NOSUID, NULL }, > { LXC_AUTO_SYS_MASK, LXC_AUTO_SYS_MIXED, "%r/sys", > "%r/sys", NULL, > MS_BIND, NULL }, > { LXC_AUTO_SYS_MASK, LXC_AUTO_SYS_MIXED, NULL, > "%r/sys", NULL, > MS_REMOUNT|MS_BIND|MS_RDONLY, NULL },
fwiw - the first one works, the second one does not due to an apparent inability to statvfs the origin. > Alternately you can read the flags off of the original mount of proc or sysfs. > > diff --git a/src/lxc/conf.c b/src/lxc/conf.c > index 9870455b3cae..50ea49973e80 100644 > --- a/src/lxc/conf.c > +++ b/src/lxc/conf.c > @@ -712,7 +712,9 @@ static unsigned long add_required_remount_flags(const > char *s, const char *d, > struct statvfs sb; > unsigned long required_flags = 0; > > - if (!(flags & MS_REMOUNT)) > + if (!(flags & MS_REMOUNT) && > + (strcmp(s, "proc") != 0) && > + (strcmp(s, "sysfs") != 0)) > return flags; > > if (!s) > > Eric > _______________________________________________ > Containers mailing list > [email protected] > https://lists.linuxfoundation.org/mailman/listinfo/containers -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
