Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264949AbUFGRpb (ORCPT ); Mon, 7 Jun 2004 13:45:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264961AbUFGRpb (ORCPT ); Mon, 7 Jun 2004 13:45:31 -0400 Received: from smtp003.mail.ukl.yahoo.com ([217.12.11.34]:44479 "HELO smtp003.mail.ukl.yahoo.com") by vger.kernel.org with SMTP id S264949AbUFGRpE (ORCPT ); Mon, 7 Jun 2004 13:45:04 -0400 From: BlaisorBlade To: Andrew Morton , Linus Torvalds Subject: [PATCH] Missing BKL in sys_chroot() for 2.6 Date: Sun, 6 Jun 2004 19:58:48 +0200 User-Agent: KMail/1.5 Cc: linux-kernel@vger.kernel.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200406061958.48262.blaisorblade_spam@yahoo.it> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2071 Lines: 63 (PLEASE cc me on replies as I'm not subscribed). Set_fs_root *claims* it wants the BKL held: /* * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values. * It can block. Requires the big lock held. */ void set_fs_root(struct fs_struct *fs, struct vfsmount *mnt, struct dentry *dentry) But sys_chroot ignores this. So I attach this patch (apply with patch -p1 -l). Maybe the solution is to kill that comment, maybe not (sys_pivot_root() calls chroot_fs_refs() -> set_fs_root() with the BKL held, but that has a lot of reasons other than this). If that comment is correct, however, it probably holds even for set_fs_altroot(), since it's similar. So this patch adds it. TESTING: none, I'm sure about the inconsistency, a lot less about the solution (no kernel manual explains the BKL, since it is a relict; except the ones who still says it blocks all the rest of the kernel, while I think it is just a recursive and "sleepable" spinlock - am I correct?). --- vanilla-linux-2.6.6/fs/open.c.saved 2004-05-10 21:37:11.000000000 +0200 +++ vanilla-linux-2.6.6/fs/open.c 2004-06-06 19:40:20.000000000 +0200 @@ -581,8 +581,13 @@ if (!capable(CAP_SYS_CHROOT)) goto dput_and_out; + lock_kernel(); + set_fs_root(current->fs, nd.mnt, nd.dentry); set_fs_altroot(); + + unlock_kernel(); + error = 0; dput_and_out: path_release(&nd); --- vanilla-linux-2.6.6/fs/namei.c.saved 2004-05-10 21:37:09.000000000 +0200 +++ vanilla-linux-2.6.6/fs/namei.c 2004-06-06 19:49:25.000000000 +0200 @@ -814,6 +814,9 @@ return 1; } +/* + * Requires the big lock held. + */ void set_fs_altroot(void) { char *emul = __emul_prefix(); -- Paolo Giarrusso, aka Blaisorblade Linux registered user n. 292729 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/