This is a note to let you know that I've just added the patch titled
kernfs: protect lazy kernfs_iattrs allocation with mutex
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kernfs-protect-lazy-kernfs_iattrs-allocation-with-mutex.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4afddd60a770560d370d6f85c5aef57c16bf7502 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@xxxxxxxxxx>
Date: Wed, 2 Apr 2014 16:40:52 -0400
Subject: kernfs: protect lazy kernfs_iattrs allocation with mutex
From: Tejun Heo <tj@xxxxxxxxxx>
commit 4afddd60a770560d370d6f85c5aef57c16bf7502 upstream.
kernfs_iattrs is allocated lazily when operations which require it
take place; unfortunately, the lazy allocation and returning weren't
properly synchronized and when there are multiple concurrent
operations, it might end up returning kernfs_iattrs which hasn't
finished initialization yet or different copies to different callers.
Fix it by synchronizing with a mutex. This can be smarter with memory
barriers but let's go there if it actually turns out to be necessary.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Link: http://lkml.kernel.org/g/533ABA32.9080602@xxxxxxxxxx
Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/kernfs/inode.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -48,14 +48,18 @@ void __init kernfs_inode_init(void)
static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
{
+ static DEFINE_MUTEX(iattr_mutex);
+ struct kernfs_iattrs *ret;
struct iattr *iattrs;
+ mutex_lock(&iattr_mutex);
+
if (kn->iattr)
- return kn->iattr;
+ goto out_unlock;
kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
if (!kn->iattr)
- return NULL;
+ goto out_unlock;
iattrs = &kn->iattr->ia_iattr;
/* assign default attributes */
@@ -65,8 +69,10 @@ static struct kernfs_iattrs *kernfs_iatt
iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
simple_xattrs_init(&kn->iattr->xattrs);
-
- return kn->iattr;
+out_unlock:
+ ret = kn->iattr;
+ mutex_unlock(&iattr_mutex);
+ return ret;
}
static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
Patches currently in stable-queue which might be from tj@xxxxxxxxxx are
queue-3.14/backing_dev-fix-hung-task-on-sync.patch
queue-3.14/bdi-avoid-oops-on-device-removal.patch
queue-3.14/kernfs-protect-lazy-kernfs_iattrs-allocation-with-mutex.patch
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