linux-kernel - Re: [PATCHv3] locks: prevent side-effects of locks_release_private before file

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Date:	Fri, 27 Jul 2012 16:45:52 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Filipe Brandenburger <filbranden@...il.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>, Matthew Wilcox <matthew@....cx>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3] locks: prevent side-effects of locks_release_private
 before file_lock is initialized

On Fri, Jul 27, 2012 at 12:42:52AM -0400, Filipe Brandenburger wrote:
> When calling fcntl(fd, F_SETLEASE, lck) [with lck=F_WRLCK or F_RDLCK],
> the custom signal or owner (if any were previously set using F_SETSIG
> or F_SETOWN fcntls) would be reset when F_SETLEASE was called for the
> second time on the same file descriptor.
> 
> This bug is a regression of 2.6.37 and is described here:
> https://bugzilla.kernel.org/show_bug.cgi?id=43336
> 
> This patch reverts a commit from Oct 2004 (with subject "nfs4 lease:
> move the f_delown processing") which originally introduced the
> lm_release_private callback.

Looks fine, thanks.  I think can also do something like the following
(on top of your patch).

--b.

commit 96d6d59ceaeaacba4088862f3c57fcd011f52832
Author: J. Bruce Fields <bfields@...hat.com>
Date:   Fri Jul 27 16:18:00 2012 -0400

    locks: move lease-specific code out of locks_delete_lock
    
    No point putting something only used by one caller into common code.
    
    Signed-off-by: J. Bruce Fields <bfields@...hat.com>

diff --git a/fs/locks.c b/fs/locks.c
index 86668dd..541075a 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -570,12 +570,6 @@ static void locks_delete_lock(struct file_lock **thisfl_p)
 	fl->fl_next = NULL;
 	list_del_init(&fl->fl_link);
 
-	fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
-	if (fl->fl_fasync != NULL) {
-		printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
-		fl->fl_fasync = NULL;
-	}
-
 	if (fl->fl_nspid) {
 		put_pid(fl->fl_nspid);
 		fl->fl_nspid = NULL;
@@ -1150,6 +1144,11 @@ int lease_modify(struct file_lock **before, int arg)
 
 		f_delown(filp);
 		filp->f_owner.signum = 0;
+		fasync_helper(0, fl->fl_file, 0, &fl->fl_fasync);
+		if (fl->fl_fasync != NULL) {
+			printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
+			fl->fl_fasync = NULL;
+		}
 		locks_delete_lock(before);
 	}
 	return 0;
--
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