Herbert Poetzl wrote: > On Sun, Jun 17, 2007 at 06:38:30PM +0400, Oleg Nesterov wrote: >> On 06/16, Herbert Poetzl wrote: >>> On Tue, May 08, 2007 at 07:45:35PM -0700, akpm@xxxxxxxxxxxxxxxxxxxx wrote: >>>> The patch titled >>>> Merge sys_clone()/sys_unshare() nsproxy and namespace handling >>>> has been removed from the -mm tree. Its filename was >>>> merge-sys_clone-sys_unshare-nsproxy-and-namespace.patch >>>> >>>> This patch was dropped because it was merged into mainline or a subsystem tree >>>> >>> .. [zapped] ... >>> >>>> + * Called from unshare. Unshare all the namespaces part of nsproxy. >>>> + * On sucess, returns the new nsproxy and a reference to old nsproxy >>>> + * to make sure it stays around. >>>> + */ >>>> +int unshare_nsproxy_namespaces(unsigned long unshare_flags, >>>> + struct nsproxy **new_nsp, struct fs_struct *new_fs) >>>> +{ >>> this makes sys_unshare leak and nsproxy (reference) >>> >>> can be tested with the following command sequence: >>> vcmd -nu ^17 -- vcmd -nu ^17 -- sleep 10 >> I know almost nothing about this stuff, could you please explain in >> brief what this command does ... > > yeah, sure, it basically calls sys_unshare() with > bit 17 (CLONE_NEWNS) set then invokes the chained > command, so we get a sleep which is in a separate > namespace, unshared from a namespace != the main > one ... > >> ... and how do you detect a leak? > >>> (and some nsproxy accounting/debugging as used in >>> Linux-VServer) > > on Linux-VServer,we have accounting for those > proxies (and several other namespace related stuff) > because we already suspected leakage and reference > bugs in this area some time ago ... btw, I also > suggested to put a similar functionality in mainline > for the time being, but it was ignored, as usual ... > >>> we probably want to drop the reference to the old >>> nsproxy in sys_unshare() but I do not see a good reason >>> to take the reference in the first place (at least not >>> with the code in mainline 2.6.22-rc4) >> At first glance, sys_unshare() drops the reference to >> the old nsproxy, > > okay, the 'current' task has an nsproxy, and keeps > a reference to that (let's assume it is the only > task using this nsproxy, then the count will be 1) > > unshare_nsproxy_namespaces() now does get_nsproxy() > which makes the count=2, then it creates a new > nsproxy (which will get count=1), and returns ... > >> old_nsproxy = current->nsproxy; >> current->nsproxy = new_nsproxy; >> new_nsproxy = old_nsproxy; > > sys_unshare, now replaces the current->nsproxy with > the new one, which will have the correct count=1, > and puts the old nsproxy (which has count=2), and > thus the nsproxy will not get released, although > it isn't referenced/used anymore ... Herbert, Could you give a try to the patch i've sent previously and this one which removes an extra get_nsproxy() ? It fixes the leak for me. I've run the ltp tests we have on namespace unsharing and i could see the no leaks in /proc/slabinfo. Badari, That extra get_nsproxy() seemed a superfluous remain from the 2.6.20. Do you see any issues with it ? If we're all happy with these fixes, i'll send them on lkml@ for review. They might deserve to be in 2.6.22. Thanks, C. Signed-off-by: Cedric Le Goater <clg@xxxxxxxxxx> --- kernel/nsproxy.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) Index: 2.6.22-rc4-mm2/kernel/nsproxy.c =================================================================== --- 2.6.22-rc4-mm2.orig/kernel/nsproxy.c +++ 2.6.22-rc4-mm2/kernel/nsproxy.c @@ -175,7 +175,6 @@ void free_nsproxy(struct nsproxy *ns) int unshare_nsproxy_namespaces(unsigned long unshare_flags, struct nsproxy **new_nsp, struct fs_struct *new_fs) { - struct nsproxy *old_ns = current->nsproxy; int err = 0; if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC | @@ -185,14 +184,10 @@ int unshare_nsproxy_namespaces(unsigned if (!capable(CAP_SYS_ADMIN)) return -EPERM; - get_nsproxy(old_ns); - *new_nsp = create_new_namespaces(unshare_flags, current, new_fs ? new_fs : current->fs); - if (IS_ERR(*new_nsp)) { + if (IS_ERR(*new_nsp)) err = PTR_ERR(*new_nsp); - put_nsproxy(old_ns); - } return err; } _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers