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[82.59.6.76]) by smtp.gmail.com with ESMTPSA id fi5sm1290151ejc.43.2021.02.24.05.21.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Feb 2021 05:21:40 -0800 (PST) Date: Wed, 24 Feb 2021 14:21:33 +0100 From: Andrea Parri To: Sasha Levin Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Juan Vazquez , Michael Kelley , Wei Liu , linux-hyperv@vger.kernel.org Subject: Re: [PATCH AUTOSEL 4.19 21/26] Drivers: hv: vmbus: Resolve race condition in vmbus_onoffer_rescind() Message-ID: <20210224132133.GA2031@anparri> References: <20210224125435.483539-1-sashal@kernel.org> <20210224125435.483539-21-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210224125435.483539-21-sashal@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On Wed, Feb 24, 2021 at 07:54:29AM -0500, Sasha Levin wrote: > From: "Andrea Parri (Microsoft)" > > [ Upstream commit e4d221b42354b2e2ddb9187a806afb651eee2cda ] > > An erroneous or malicious host could send multiple rescind messages for > a same channel. In vmbus_onoffer_rescind(), the guest maps the channel > ID to obtain a pointer to the channel object and it eventually releases > such object and associated data. The host could time rescind messages > and lead to an use-after-free. Add a new flag to the channel structure > to make sure that only one instance of vmbus_onoffer_rescind() can get > the reference to the channel object. > > Reported-by: Juan Vazquez > Signed-off-by: Andrea Parri (Microsoft) > Reviewed-by: Michael Kelley > Link: https://lore.kernel.org/r/20201209070827.29335-6-parri.andrea@gmail.com > Signed-off-by: Wei Liu > Signed-off-by: Sasha Levin Same here. Andrea > --- > drivers/hv/channel_mgmt.c | 12 ++++++++++++ > include/linux/hyperv.h | 1 + > 2 files changed, 13 insertions(+) > > diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c > index 7920b0d7e35a7..1322e799938af 100644 > --- a/drivers/hv/channel_mgmt.c > +++ b/drivers/hv/channel_mgmt.c > @@ -954,6 +954,18 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr) > > mutex_lock(&vmbus_connection.channel_mutex); > channel = relid2channel(rescind->child_relid); > + if (channel != NULL) { > + /* > + * Guarantee that no other instance of vmbus_onoffer_rescind() > + * has got a reference to the channel object. Synchronize on > + * &vmbus_connection.channel_mutex. > + */ > + if (channel->rescind_ref) { > + mutex_unlock(&vmbus_connection.channel_mutex); > + return; > + } > + channel->rescind_ref = true; > + } > mutex_unlock(&vmbus_connection.channel_mutex); > > if (channel == NULL) { > diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h > index 35461d49d3aee..59525fe25abde 100644 > --- a/include/linux/hyperv.h > +++ b/include/linux/hyperv.h > @@ -736,6 +736,7 @@ struct vmbus_channel { > u8 monitor_bit; > > bool rescind; /* got rescind msg */ > + bool rescind_ref; /* got rescind msg, got channel reference */ > struct completion rescind_event; > > u32 ringbuffer_gpadlhandle; > -- > 2.27.0 >