Messages in this thread Patch in this message | | | Date | Thu, 9 Jan 2014 10:51:14 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH] SELinux: Fix possible NULL pointer dereference in selinux_inode_permission() |
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On Thu, 9 Jan 2014 10:31:55 -0500 Eric Paris <eparis@parisplace.org> wrote:
> Didn't Al find this/something very similar. I really hate this
I'm not involved with the vfs, so I'm unaware of other solutions presented. I just hit this now and solving bugs is where I get a chance to learn about other aspects of the kernel. ;-)
> solution. Why should every LSM try to understand the intimate > lifetime rules of the parent subsystems? The real problem is that > inode_free_security() is being called while the inode is still in use. > While I agree with the assessment, I disagree with the solution. Let > me try to find where Al and Christoph talked about this.... >
The other obvious solution (but not as trivial to implement) is to call the security_inode_free() and friends (probably __destroy_inode() itself) after a synchronize_rcu().
Perhaps something like this?
-- Steve
diff --git a/fs/inode.c b/fs/inode.c index 4bcdad3..a8f3b88 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -252,16 +252,17 @@ EXPORT_SYMBOL(__destroy_inode); static void i_callback(struct rcu_head *head) { struct inode *inode = container_of(head, struct inode, i_rcu); + __destroy_inode(inode); kmem_cache_free(inode_cachep, inode); } static void destroy_inode(struct inode *inode) { BUG_ON(!list_empty(&inode->i_lru)); - __destroy_inode(inode); - if (inode->i_sb->s_op->destroy_inode) + if (inode->i_sb->s_op->destroy_inode) { + __destroy_inode(inode); inode->i_sb->s_op->destroy_inode(inode); - else + } else call_rcu(&inode->i_rcu, i_callback); }
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