[PATCH] pidns: Fix a leak in /proc inodes and dentries

[PATCH] pidns: Fix a leak in /proc inodes and dentries

[Sukadev Bhattiprolu]

Fix a leak in /proc dentries and inodes with pid namespaces.

This fix reverts the commit 7766755a2f249e7e0. The leak was reported by
Daniel Lezcano - see  http://lkml.org/lkml/2009/10/2/159.

To summarize the thread, when container-init is terminated, it sets the
PF_EXITING flag and then zaps all the other processes in the container.
When those processes exit, they are expected to be reaped by the container-
init and as a part of reaping, the container-init should flush any /proc
dentries associated with the processes. But because the container-init is
itself exiting and the following PF_EXITING check, the dentires are not
flushed, resulting in leak in /proc inodes and dentries.

Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Reported-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jan Kara <jack@ucw.cz>
Cc: Andrea Arcangeli <andrea@cpushare.com>

---
 fs/proc/base.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Index: linux-2.6/fs/proc/base.c
===================================================================
--- linux-2.6.orig/fs/proc/base.c	2009-10-19 20:28:51.000000000 -0700
+++ linux-2.6/fs/proc/base.c	2009-10-19 20:29:03.000000000 -0700
@@ -2580,8 +2580,7 @@ static void proc_flush_task_mnt(struct v
 	name.len = snprintf(buf, sizeof(buf), "%d", pid);
 	dentry = d_hash_and_lookup(mnt->mnt_root, &name);
 	if (dentry) {
-		if (!(current->flags & PF_EXITING))
-			shrink_dcache_parent(dentry);
+		shrink_dcache_parent(dentry);
 		d_drop(dentry);
 		dput(dentry);
 	}

Re: [PATCH] pidns: Fix a leak in /proc inodes and dentries

[Eric W. Biederman]

Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> writes:

> Fix a leak in /proc dentries and inodes with pid namespaces.
>
> This fix reverts the commit 7766755a2f249e7e0. The leak was reported by
> Daniel Lezcano - see  http://lkml.org/lkml/2009/10/2/159.
>
> To summarize the thread, when container-init is terminated, it sets the
> PF_EXITING flag and then zaps all the other processes in the container.
> When those processes exit, they are expected to be reaped by the container-
> init and as a part of reaping, the container-init should flush any /proc
> dentries associated with the processes. But because the container-init is
> itself exiting and the following PF_EXITING check, the dentires are not
> flushed, resulting in leak in /proc inodes and dentries.

Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>

> Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
> Reported-by: Daniel Lezcano <dlezcano@fr.ibm.com>
> Cc: Eric W. Biederman <ebiederm@xmission.com>
> Cc: Jan Kara <jack@ucw.cz>
> Cc: Andrea Arcangeli <andrea@cpushare.com>
>
> ---
>  fs/proc/base.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> Index: linux-2.6/fs/proc/base.c
> ===================================================================
> --- linux-2.6.orig/fs/proc/base.c	2009-10-19 20:28:51.000000000 -0700
> +++ linux-2.6/fs/proc/base.c	2009-10-19 20:29:03.000000000 -0700
> @@ -2580,8 +2580,7 @@ static void proc_flush_task_mnt(struct v
>  	name.len = snprintf(buf, sizeof(buf), "%d", pid);
>  	dentry = d_hash_and_lookup(mnt->mnt_root, &name);
>  	if (dentry) {
> -		if (!(current->flags & PF_EXITING))
> -			shrink_dcache_parent(dentry);
> +		shrink_dcache_parent(dentry);
>  		d_drop(dentry);
>  		dput(dentry);
>  	}

Re: [PATCH] pidns: Fix a leak in /proc inodes and dentries

[Cedric Le Goater]

On 10/20/2009 12:27 PM, Eric W. Biederman wrote:
> Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> writes:
> 
>> Fix a leak in /proc dentries and inodes with pid namespaces.
>>
>> This fix reverts the commit 7766755a2f249e7e0. The leak was reported by
>> Daniel Lezcano - see  http://lkml.org/lkml/2009/10/2/159.
>>
>> To summarize the thread, when container-init is terminated, it sets the
>> PF_EXITING flag and then zaps all the other processes in the container.
>> When those processes exit, they are expected to be reaped by the container-
>> init and as a part of reaping, the container-init should flush any /proc
>> dentries associated with the processes. But because the container-init is
>> itself exiting and the following PF_EXITING check, the dentires are not
>> flushed, resulting in leak in /proc inodes and dentries.
> 
> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>

there's indeed a lot of progress. A run of our C/R testsuite (spawning and
killing a few thousands pidns) used to leak ~700MB of slab, it's now gone. 
thanks suka for spending time on this. 

but we still have some minor leaks. below are contents of /proc/slabinfo 
before and after the run, you will notice that in some cases, dangling refs 
of nsproxy and pid_namespace are still alive. I wonder if there are some 
cases when this can happen, else I'll try to reproduce it.

Cheers,

C. 

* slabinfo.qemu (i686)

pid_namespace          0      0     64   59    1 
nsproxy                0      0     48   78    1 
proc_inode_cache     193    193   4096    1    1 
dentry              6734   6734   4096    1    1 

pid_2                  0      0     88   44    1 
pid_namespace          0      0     64   59    1 
nsproxy                0      0     48   78    1 
proc_inode_cache       4      4   4096    1    1 
dentry             36112  36112   4096    1    1 

* slabinfo.a13.test.meiosys.com (ppc64)

pid_namespace          0      0   4096    1    1 
nsproxy                0      0     72   53    1 
proc_inode_cache     506    513   4096    1    1 
dentry              6269   6272    280   14    1 

pid_2                  1     28    136   28    1 
pid_namespace          1      1   4096    1    1 
nsproxy                0      0     72   53    1 
proc_inode_cache     486    498   4096    1    1 
dentry             49051  49448    280   14    1 


* slabinfo.f13.test.meiosys.com (ppc64)

pid_namespace          0      0   4096    1    1 
nsproxy                0      0     72   53    1 
proc_inode_cache     248    263   4096    1    1 
dentry              7359   7364    280   14    1 

pid_2                  0      0    136   28    1 
pid_namespace          0      0   4096    1    1 
nsproxy                0      0     72   53    1 
proc_inode_cache     240    240   4096    1    1 
dentry             50253  50666    280   14    1 


* slabinfo.r3-23.test.meiosys.com (x86_64)

pid_namespace          0      0   4096    1    1 
nsproxy                0      0     72   53    1 
proc_inode_cache     479    495   4096    1    1 
dentry              5614   5614    280   14    1 

pid_2                  1     28    136   28    1 
pid_namespace          1      1   4096    1    1 
nsproxy                0      0     72   53    1 
proc_inode_cache     576    576   4096    1    1 
dentry             52202  52444    280   14    1 


* slabinfo.r3-24.test.meiosys.com (x86_64)

pid_namespace          0      0   4096    1    1 
nsproxy                0      0     72   53    1 
proc_inode_cache     464    486   4096    1    1 
dentry              5698   5698    280   14    1 

pid_2                  0      0    136   28    1 
pid_namespace          0      0   4096    1    1 
nsproxy                0      0     72   53    1 
proc_inode_cache     448    448   4096    1    1 
dentry             51845  52164    280   14    1 


* slabinfo.r3-26.test.meiosys.com (i686)

pid_namespace          0      0     64   59    1 
nsproxy                0      0     48   78    1 
proc_inode_cache     449    466   4096    1    1 
dentry              5633   5633   4096    1    1 

pid_2                  0      0     88   44    1 
pid_namespace          0      0     64   59    1 
nsproxy                0      0     48   78    1 
proc_inode_cache     448    448   4096    1    1 
dentry             52039  52039   4096    1    1 


* slabinfo.linuz12 (s390x)

pid_namespace          0      0   2112    3    2 
nsproxy                0      0     48   77    1 
proc_inode_cache     725    798    640    6    1 
dentry              4340   4340    192   20    1 

pid_2                  1     30    128   30    1 
pid_namespace          1      3   2112    3    2 
nsproxy                1     77     48   77    1 
proc_inode_cache      74    180    640    6    1 
dentry             34511  36820    192   20    1 

Re: [PATCH] pidns: Fix a leak in /proc inodes and dentries

[Alexey Dobriyan]

On Mon, Oct 19, 2009 at 09:13:37PM -0700, Sukadev Bhattiprolu wrote:
> --- linux-2.6.orig/fs/proc/base.c
> +++ linux-2.6/fs/proc/base.c
> @@ -2580,8 +2580,7 @@ static void proc_flush_task_mnt(struct v
>  	name.len = snprintf(buf, sizeof(buf), "%d", pid);
>  	dentry = d_hash_and_lookup(mnt->mnt_root, &name);
>  	if (dentry) {
> -		if (!(current->flags & PF_EXITING))
> -			shrink_dcache_parent(dentry);
> +		shrink_dcache_parent(dentry);

What to do with original deadlock?