From: "Aurélien Aptel" <aaptel@suse.com>
To: "Paulo Alcantara \(SUSE\)" <pc@cjr.nz>, smfrench@gmail.com
Cc: linux-cifs@vger.kernel.org, "Paulo Alcantara \(SUSE\)" <pc@cjr.nz>
Subject: Re: [PATCH 5/7] cifs: Fix potential deadlock when updating vol in cifs_reconnect()
Date: Mon, 25 Nov 2019 13:01:38 +0100 [thread overview]
Message-ID: <87a78kw4f1.fsf@suse.com> (raw)
In-Reply-To: <20191122153057.6608-6-pc@cjr.nz>
"Paulo Alcantara (SUSE)" <pc@cjr.nz> writes:
> We can't hold the vol_lock spinlock while refreshing the DFS cache
> because cifs_reconnect() may call dfs_cache_update_vol() while we are
> walking through the volume list.
>
> Create a temp list with all volumes eligible for refreshing and then
> use it without any locks held.
Commit msg should mention it makes the vol_info refcounted.
> Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
> ---
> fs/cifs/dfs_cache.c | 45 +++++++++++++++++++++++++++++++++------------
> 1 file changed, 33 insertions(+), 12 deletions(-)
>
> diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
> index b082603c793a..5b9d7281dd67 100644
> --- a/fs/cifs/dfs_cache.c
> +++ b/fs/cifs/dfs_cache.c
> @@ -49,6 +49,8 @@ struct vol_info {
> struct smb_vol smb_vol;
> char *mntdata;
> struct list_head list;
> + struct list_head rlist;
> + int vol_count;
> };
>
> static struct kmem_cache *cache_slab __read_mostly;
> @@ -516,13 +518,15 @@ static struct cache_entry *lookup_cache_entry(const char *path,
> return ce;
> }
>
> -static inline void free_vol(struct vol_info *vi)
> +static void put_vol(struct vol_info *vi)
> {
> - list_del(&vi->list);
> - kfree(vi->fullpath);
> - kfree(vi->mntdata);
> - cifs_cleanup_volume_info_contents(&vi->smb_vol);
> - kfree(vi);
> + if (!--vi->vol_count) {
> + list_del_init(&vi->list);
> + kfree(vi->fullpath);
> + kfree(vi->mntdata);
> + cifs_cleanup_volume_info_contents(&vi->smb_vol);
> + kfree(vi);
> + }
> }
Can we document that put_vol() assumes vol_lock is held?
--
Aurélien Aptel / SUSE Labs Samba Team
GPG: 1839 CB5F 9F5B FB9B AA97 8C99 03C8 A49B 521B D5D3
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, DE
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 247165 (AG München)
next prev parent reply other threads:[~2019-11-25 12:01 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-22 15:30 [PATCH 0/7] DFS fixes Paulo Alcantara (SUSE)
2019-11-22 15:30 ` [PATCH 1/7] cifs: Fix use-after-free bug in cifs_reconnect() Paulo Alcantara (SUSE)
2019-11-25 7:34 ` Steve French
2019-11-25 11:36 ` Aurélien Aptel
2019-11-22 15:30 ` [PATCH 2/7] cifs: Fix lookup of root ses in DFS referral cache Paulo Alcantara (SUSE)
2019-11-25 7:33 ` Steve French
2019-11-25 11:37 ` Aurélien Aptel
2019-11-22 15:30 ` [PATCH 3/7] cifs: Fix potential softlockups while refreshing DFS cache Paulo Alcantara (SUSE)
2019-11-25 11:41 ` Aurélien Aptel
2019-11-25 15:35 ` Steve French
2019-11-25 19:53 ` Pavel Shilovsky
2019-11-22 15:30 ` [PATCH 4/7] cifs: Clean up DFS referral cache Paulo Alcantara (SUSE)
2019-11-25 11:54 ` Aurélien Aptel
2019-11-22 15:30 ` [PATCH 5/7] cifs: Fix potential deadlock when updating vol in cifs_reconnect() Paulo Alcantara (SUSE)
2019-11-25 12:01 ` Aurélien Aptel [this message]
2019-11-22 15:30 ` [PATCH 6/7] cifs: Fix retrieval of DFS referrals in cifs_mount() Paulo Alcantara (SUSE)
2019-11-25 7:38 ` Steve French
2019-11-22 15:30 ` [PATCH 7/7] cifs: Always update signing key of first channel Paulo Alcantara (SUSE)
2019-11-25 15:48 ` Aurélien Aptel
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