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bh=I5eMpr2L+oDdbAVnMFYihTm1RKGCWAkzGk6JihsOgwQ=; b=gfVpklRWF9dnGo3ZjUOZ1OnGviTIquQfsGNjAQ2sx6CYWQ9QOYb5ap8lMGhIPSLt55qlOU t6cihi4KsXMBuawzNaXrDap+AtzEmCbCoWig7Y4PX9TaWieyPCWDTPPKfL38hL9XU4CoHA RhehwCoce2cMrF1tMf9ghgiX42CoY7Q= X-MC-Unique: qcWGqic5OH2ogHhqfJTogw-1 From: Eric Auger To: eric.auger.pro@gmail.com, eric.auger@redhat.com, mst@redhat.com, qemu-devel@nongnu.org Cc: jasowang@redhat.com, lvivier@redhat.com Subject: [PATCH] vhost: Add a defensive check in vhost_commit against wrong deallocation Date: Wed, 13 Sep 2023 09:46:57 +0200 Message-ID: <20230913074657.523530-1-eric.auger@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=eric.auger@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1694591280690100001 Content-Type: text/plain; charset="utf-8" In vhost_commit(), it may happen that dev->mem_sections and dev->tmp_sections are equal, in which case, unconditionally freeing old_sections at the end of the function will also free dev->mem_sections used on subsequent call leading to a segmentation fault. Check this situation before deallocating memory. Signed-off-by: Eric Auger Fixes: c44317efecb2 ("vhost: Build temporary section list and deref after commit") CC: QEMU Stable --- This SIGSEV condition can be reproduced with https://lore.kernel.org/all/20230904080451.424731-1-eric.auger@redhat.com/#r This is most probably happening in a situation where the memory API is used in a wrong manner but well. --- hw/virtio/vhost.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c index e2f6ffb446..c02c599ef0 100644 --- a/hw/virtio/vhost.c +++ b/hw/virtio/vhost.c @@ -545,6 +545,11 @@ static void vhost_commit(MemoryListener *listener) dev->mem_sections =3D dev->tmp_sections; dev->n_mem_sections =3D dev->n_tmp_sections; =20 + if (old_sections =3D=3D dev->mem_sections) { + assert(n_old_sections =3D=3D dev->n_mem_sections); + return; + } + if (dev->n_mem_sections !=3D n_old_sections) { changed =3D true; } else { --=20 2.41.0