From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Howells Subject: Re: [AFS] prevent double cell registration Date: Tue, 25 Mar 2008 19:05:44 +0000 Message-ID: <29905.1206471944@redhat.com> References: <87skye7lyh.fsf@apollo.bitebene.org> <868x0bog65.fsf@deprecated.bitebene.org> <27146.1206465784@redhat.com> Cc: dhowells@redhat.com, linux-fsdevel@vger.kernel.org To: Sven Schnelle Return-path: Received: from mx1.redhat.com ([66.187.233.31]:36469 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755798AbYCYTFt (ORCPT ); Tue, 25 Mar 2008 15:05:49 -0400 In-Reply-To: <87skye7lyh.fsf@apollo.bitebene.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Your patch needs a bit of adjustment. The check must be done inside the write lock on afs_cells_sem otherwise there's a race. David --- AFS: prevent double cell registration From: Sven Schnelle kafs doesn't check if the cell already exists - so if you do an echo "add newcell.org 1.2.3.4" >/proc/fs/afs/cells it will try to create this cell again. kobject will also complain about a double registration. To prevent such problems, return -EEXIST in that case. Signed-off-by: Sven Schnelle Signed-off-by: David Howells --- fs/afs/cell.c | 15 +++++++++++++-- 1 files changed, 13 insertions(+), 2 deletions(-) diff --git a/fs/afs/cell.c b/fs/afs/cell.c index 970d38f..788865d 100644 --- a/fs/afs/cell.c +++ b/fs/afs/cell.c @@ -127,14 +127,20 @@ struct afs_cell *afs_cell_create(const char *name, char *vllist) _enter("%s,%s", name, vllist); + down_write(&afs_cells_sem); + read_lock(&afs_cells_lock); + list_for_each_entry(cell, &afs_cells, link) { + if (strcasecmp(cell->name, name) == 0) + goto duplicate_name; + } + read_unlock(&afs_cells_lock); + cell = afs_cell_alloc(name, vllist); if (IS_ERR(cell)) { _leave(" = %ld", PTR_ERR(cell)); return cell; } - down_write(&afs_cells_sem); - /* add a proc directory for this cell */ ret = afs_proc_cell_setup(cell); if (ret < 0) @@ -167,6 +173,11 @@ error: kfree(cell); _leave(" = %d", ret); return ERR_PTR(ret); + +duplicate_name: + read_unlock(&afs_cells_lock); + up_write(&afs_cells_sem); + return ERR_PTR(-EEXIST); } /*