linux-kernel - RE: [PATCH] kernfs: fix dentry unexpected skip

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Date:   Mon, 21 May 2018 05:46:31 +0000
From:   "Hatayama, Daisuke" <d.hatayama@...fujitsu.com>
To:     "'gregkh@...uxfoundation.org'" <gregkh@...uxfoundation.org>
CC:     "Okajima, Toshiyuki" <toshi.okajima@...fujitsu.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "'ebiederm@...stanetworks.com'" <ebiederm@...stanetworks.com>
Subject: RE: [PATCH] kernfs: fix dentry unexpected skip



> -----Original Message-----
> From: linux-kernel-owner@...r.kernel.org
> [mailto:linux-kernel-owner@...r.kernel.org] On Behalf Of Hatayama, Daisuke
> Sent: Saturday, May 19, 2018 12:43 AM
> To: 'gregkh@...uxfoundation.org' <gregkh@...uxfoundation.org>
> Cc: Okajima, Toshiyuki/岡嶋 寿行 <toshi.okajima@...fujitsu.com>;
> linux-kernel@...r.kernel.org; 'ebiederm@...stanetworks.com'
> <ebiederm@...stanetworks.com>
> Subject: [PATCH] kernfs: fix dentry unexpected skip
> 
> kernfs_dir_next_pos() overlooks the situation that the dentry
> corresponding to a given pos object has already been inactive. Hence,
> when kernfs_dir_pos() returns the dentry with a hash value larger than
> the original one, kernfs_dir_next_pos() returns the dentry next to the
> one returned by kernfs_dir_pos(). As a result, the dentry returned by
> kernfs_dir_pos() is skipped.
> 
> To fix this issue, try to find a next node only when the returned
> object has a hash value equal to or smaller than the original one.
> 
> Signed-off-by: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
> Suggested-by: Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
> Cc: Eric W. Biederman <ebiederm@...stanetworks.com>
> ---
>  fs/kernfs/dir.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
> index 89d1dc1..8a2f49c 100644
> --- a/fs/kernfs/dir.c
> +++ b/fs/kernfs/dir.c
> @@ -1622,7 +1622,7 @@ static int kernfs_dir_fop_release(struct inode *inode,
> struct file *filp)
>  	struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos)
>  {
>  	pos = kernfs_dir_pos(ns, parent, ino, pos);
> -	if (pos) {
> +	if (pos && pos->hash <= ino) {

I found this condition still misses the case that the returend pos with
the same hash value but with different name is skipped. I'll post
v2 patch.

>  		do {
>  			struct rb_node *node = rb_next(&pos->rb);
>  			if (!node)
> --
> 1.7.1
> 
> 
>