linux-kernel - Re: [Suggestion] fs/namespace.c: the direct cause of the warning for: "ida_remove called for id=0 which is not allocated" with mnt_release_group

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Date:	Fri, 24 May 2013 09:26:47 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Al Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Takashi Iwai <tiwai@...e.de>
Subject: Re: [Suggestion] fs/namespace.c: the direct cause of the warning
 for: "ida_remove called for id=0 which is not allocated" with mnt_release_group_id()

On 05/24/2013 07:18 AM, Andrew Morton wrote:
> On Tue, 14 May 2013 17:06:30 +0800 Chen Gang <gang.chen@...anux.com> wrote:
> 
>> > After call collect_mounts(), then call drop_collected_mounts(), it will
>> > report an warning: "ida_remove called for id=0 which is not allocated"
>> > (one sample is audit_add_tree_rule() in kernel/audit_tree.c).
>> > 
>> > The direct cause (maybe also be the root cause):
>> >   collect_mounts() passs 'CL_PRIVATE' to copy_tree() -> clone_mnt().
>> >   it will set "mnt->mnt_group_id = 0" in clone_mnt().
>> >   when drop_collected_mounts() -> mnt_release_group_id(), 'mnt->mnt_group_id == 0'.
> I expect this patch also addresses the bug.  Can you please review and test it?
> 

I am sure, after apply the patch below, it will be no warning again (fix
the direct cause).

Originally, I want to fix this bug just like the patch below, but I am
not quite sure whether it will hide the real root cause.


Thanks.

> 
> From: Takashi Iwai <tiwai@...e.de>
> Subject: vfs: fix invalid ida_remove() call
> 
> When the group id of a shared mount is not allocated, the umount still
> tries to call mnt_release_group_id(), which eventually hits a kernel
> warning at ida_remove() spewing a message like:
> 
>   ida_remove called for id=0 which is not allocated.
> 
> This patch fixes the bug simply checking the group id in the caller.
> 
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> Reported-by: Cristian Rodr�guez <crrodriguez@...nsuse.org>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
> 
>  fs/pnode.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff -puN fs/pnode.c~vfs-fix-invalid-ida_remove-call fs/pnode.c
> --- a/fs/pnode.c~vfs-fix-invalid-ida_remove-call
> +++ a/fs/pnode.c
> @@ -83,7 +83,8 @@ static int do_make_slave(struct mount *m
>  		if (peer_mnt == mnt)
>  			peer_mnt = NULL;
>  	}
> -	if (IS_MNT_SHARED(mnt) && list_empty(&mnt->mnt_share))
> +	if (mnt->mnt_group_id && IS_MNT_SHARED(mnt) &&
> +	    list_empty(&mnt->mnt_share))
>  		mnt_release_group_id(mnt);
>  
>  	list_del_init(&mnt->mnt_share);
> _
> 
> 
> 


-- 
Chen Gang

Asianux Corporation
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