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 v3 08/11] cifs: Fix potential deadlock when updating vol in cifs_reconnect()
Date: Wed, 27 Nov 2019 13:09:04 +0100 [thread overview]
Message-ID: <871rttv7vj.fsf@suse.com> (raw)
In-Reply-To: <20191127003634.14072-9-pc@cjr.nz>
"Paulo Alcantara (SUSE)" <pc@cjr.nz> writes:
> We can't acquire vol_lock while refreshing the DFS cache because
> cifs_reconnect() may call dfs_cache_update_vol() while we are walking
> through the volume list.
>
> To prevent that, make vol_info refcounted, create a temp list with all
> volumes eligible for refreshing, and then use it without any locks
> held.
>
> Also turn vol_lock into a spinlock rather than a mutex.
>
> Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
> ---
> fs/cifs/dfs_cache.c | 104 +++++++++++++++++++++++++++++---------------
> 1 file changed, 69 insertions(+), 35 deletions(-)
>
> diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
> index 1d1f7c03931b..629190926197 100644
> --- a/fs/cifs/dfs_cache.c
> +++ b/fs/cifs/dfs_cache.c
> @@ -52,12 +52,14 @@ struct vol_info {
> struct smb_vol smb_vol;
> char *mntdata;
> struct list_head list;
> + struct list_head rlist;
> + int vol_count;
> };
If vol_count is going to be accessed/modified from multiple threads
without locks there might be races. I think you should use kref
https://www.kernel.org/doc/Documentation/kref.txt
--
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:[~2019-11-27 12:09 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 0:36 [PATCH v3 00/11] DFS fixes Paulo Alcantara (SUSE)
2019-11-27 0:36 ` [PATCH v3 01/11] cifs: Fix use-after-free bug in cifs_reconnect() Paulo Alcantara (SUSE)
2019-11-27 0:36 ` [PATCH v3 02/11] cifs: Fix lookup of root ses in DFS referral cache Paulo Alcantara (SUSE)
2019-11-27 0:36 ` [PATCH v3 03/11] cifs: Fix potential softlockups while refreshing DFS cache Paulo Alcantara (SUSE)
2019-11-27 0:36 ` [PATCH v3 04/11] cifs: Clean up DFS referral cache Paulo Alcantara (SUSE)
2019-11-27 11:32 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 05/11] cifs: Get rid of kstrdup_const()'d paths Paulo Alcantara (SUSE)
2019-11-27 11:33 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 06/11] cifs: Introduce helpers for finding TCP connection Paulo Alcantara (SUSE)
2019-11-27 11:33 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 07/11] cifs: Merge is_path_valid() into get_normalized_path() Paulo Alcantara (SUSE)
2019-11-27 11:34 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 08/11] cifs: Fix potential deadlock when updating vol in cifs_reconnect() Paulo Alcantara (SUSE)
2019-11-27 12:09 ` Aurélien Aptel [this message]
2019-11-27 0:36 ` [PATCH v3 09/11] cifs: Avoid doing network I/O while holding cache lock Paulo Alcantara (SUSE)
2019-11-27 13:32 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 10/11] cifs: Fix retrieval of DFS referrals in cifs_mount() Paulo Alcantara (SUSE)
2019-11-27 13:33 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 11/11] cifs: Always update signing key of first channel Paulo Alcantara (SUSE)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=871rttv7vj.fsf@suse.com \
--to=aaptel@suse.com \
--cc=linux-cifs@vger.kernel.org \
--cc=pc@cjr.nz \
--cc=smfrench@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).