From: ebiederm@xmission.com (Eric W. Biederman)
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: linux-kernel@vger.kernel.org, serge@hallyn.com, tycho@tycho.ws,
Linux Containers <containers@lists.linux-foundation.org>
Subject: [PATCH 3/5] userns: Don't read extents twice in m_start
Date: Tue, 31 Oct 2017 18:48:17 -0500 [thread overview]
Message-ID: <87k1zaswu6.fsf_-_@xmission.com> (raw)
In-Reply-To: <871sliubhj.fsf_-_@xmission.com> (Eric W. Biederman's message of "Tue, 31 Oct 2017 18:46:32 -0500")
This is important so reading /proc/<pid>/{uid_map,gid_map,projid_map} while
the map is being written does not do strange things.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
kernel/user_namespace.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 563a2981d7c7..4f7e357ac1e2 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -683,11 +683,13 @@ static void *m_start(struct seq_file *seq, loff_t *ppos,
struct uid_gid_map *map)
{
loff_t pos = *ppos;
+ unsigned extents = map->nr_extents;
+ smp_rmb();
- if (pos >= map->nr_extents)
+ if (pos >= extents)
return NULL;
- if (map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
+ if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
return &map->extent[pos];
return &map->forward[pos];
--
2.14.1
next prev parent reply other threads:[~2017-10-31 23:48 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-24 22:04 [PATCH 1/2 v6] user namespace: use union in {g,u}idmap struct Christian Brauner
2017-10-24 22:04 ` [PATCH 2/2 v6] user namespaces: bump idmap limits to 340 Christian Brauner
2017-10-31 23:46 ` [PATCH 0/5] userns: bump idmap limits, fixes & tweaks Eric W. Biederman
2017-10-31 23:47 ` [PATCH 1/5] userns: Don't special case a count of 0 Eric W. Biederman
2017-10-31 23:47 ` [PATCH 2/5] userns: Simplify the user and group mapping functions Eric W. Biederman
2017-10-31 23:48 ` Eric W. Biederman [this message]
2017-11-01 8:31 ` [PATCH 3/5] userns: Don't read extents twice in m_start Nikolay Borisov
2017-11-01 11:08 ` Eric W. Biederman
2017-11-01 13:05 ` Nikolay Borisov
2017-11-01 13:05 ` Peter Zijlstra
2017-11-01 14:01 ` Christian Brauner
2017-11-01 14:16 ` Peter Zijlstra
2017-11-01 16:29 ` Christian Brauner
2017-11-01 16:31 ` Christian Brauner
2017-11-01 17:00 ` Joe Perches
2017-11-01 17:20 ` Eric W. Biederman
2017-11-01 18:15 ` Peter Zijlstra
2017-10-31 23:48 ` [PATCH 4/5] userns: Make map_id_down a wrapper for map_id_range_down Eric W. Biederman
2017-10-31 23:49 ` [PATCH 5/5] userns: Simplify insert_extent Eric W. Biederman
2017-11-01 10:51 ` [PATCH 0/5] userns: bump idmap limits, fixes & tweaks Christian Brauner
2017-11-01 11:15 ` Eric W. Biederman
2017-11-01 13:31 ` Christian Brauner
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=87k1zaswu6.fsf_-_@xmission.com \
--to=ebiederm@xmission.com \
--cc=christian.brauner@ubuntu.com \
--cc=containers@lists.linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=serge@hallyn.com \
--cc=tycho@tycho.ws \
/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