From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: Re: proto_unregister sleeps while atomic Date: Wed, 07 Sep 2005 01:42:48 +0200 Message-ID: <431E2978.2030701@trash.net> References: <200509070026.34999.daniele@orlandi.com> <431E1FE9.7030405@trash.net> <20050906.160728.25203864.davem@davemloft.net> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------030301070001070006070403" Cc: daniele@orlandi.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Return-path: To: "David S. Miller" In-Reply-To: <20050906.160728.25203864.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org This is a multi-part message in MIME format. --------------030301070001070006070403 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit David S. Miller wrote: > From: Patrick McHardy > Date: Wed, 07 Sep 2005 01:02:01 +0200 > > >>You're right, good catch. This patch fixes it by moving the lock >>down to the list-operation which it is supposed to protect. > > > I think we need to unlink from the list first if you're > going to do it this way. Otherwise someone can find the > protocol via lookup, and then bogusly try to use the SLAB > cache we're freeing up. > > Or does something else prevent this? The only other user of proto_list besides proto_register, which doesn't care, are the seqfs functions. They use the slab pointer, but in a harmless way: proto->slab == NULL ? "no" : "yes", Anyway, I've moved it up to the top. --------------030301070001070006070403 Content-Type: text/plain; name="x" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="x" [NET]: proto_unregister: fix sleeping while atomic proto_unregister holds a lock while calling kmem_cache_destroy, which can sleep. Noticed by Daniele Orlandi . Signed-off-by: Patrick McHardy --- commit d68b08edb26dfb58d18ab6c555d011572f9115a6 tree 1d14cf91ca5db6878b6af3953f85a34a6fe12a91 parent 591bd554f58b7d363167760a606d2a84696772da author Patrick McHardy Wed, 07 Sep 2005 01:35:19 +0200 committer Patrick McHardy Wed, 07 Sep 2005 01:35:19 +0200 net/core/sock.c | 5 ++--- 1 files changed, 2 insertions(+), 3 deletions(-) diff --git a/net/core/sock.c b/net/core/sock.c --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1529,6 +1529,8 @@ EXPORT_SYMBOL(proto_register); void proto_unregister(struct proto *prot) { write_lock(&proto_list_lock); + list_del(&prot->node); + write_unlock(&proto_list_lock); if (prot->slab != NULL) { kmem_cache_destroy(prot->slab); @@ -1550,9 +1552,6 @@ void proto_unregister(struct proto *prot kfree(name); prot->twsk_slab = NULL; } - - list_del(&prot->node); - write_unlock(&proto_list_lock); } EXPORT_SYMBOL(proto_unregister); --------------030301070001070006070403--