Introduce a read-only `tapfd` element for direct interfaces (macvtap), which contains the path to the backing tapfd for that interface (e.g. `/dev/tapXX`). The element is only included when the domain is being formatted for internal consumption (VIR_DOMAIN_DEF_FORMAT_STATUS) and is not accepted in user-provided XML (!VIR_DOMAIN_DEF_PARSE_INACTIVE). This is used by the AppArmor security driver when re-generating profiles. Partial-Resolves: #692 Bug-Ubuntu: https://bugs.launchpad.net/bugs/2126574 Signed-off-by: Wesley Hershberger <wesley.hershberger@canonical.com> --- This submission is a partial revision of a previous series with a fix for the macvtap component of gitlab#692 [1][2]. I haven't had bandwidth to resolve the blockcommit component since the complexity there is somewhat higher (and is also lower priority for us). I kept the separate `tapfd` element rather than reusing the existing `backend` element (virDomainNetBackend.tap) to avoid making a user-visible change [3]. I'd be happy to use the existing field instead if you think that would make more sense. I opted not to introduce/modify a security driver API for FD+path as the patch here is sufficient to resolve the bug, but would be willing to do so if that would make this change more palatable. I've opened a MR to libvirt-tck with test cases that demonstrate the bugs that this fixes [4]. apparmor/110-macvtap.t passes with this patch applied. Thanks for the reviews and continued consideration. ~Wesley [1] https://lists.libvirt.org/archives/list/devel@lists.libvirt.org/thread/UNNBQ... [2] https://gitlab.com/libvirt/libvirt/-/issues/692 [3] https://libvirt.org/formatdomain.html#setting-network-backend-specific-optio... [4] https://gitlab.com/libvirt/libvirt-tck/-/merge_requests/73 --- Changes in v2: - Drop `virt-aa-helper: Ask for no deny rule...` as it was applied - Drop `qemu: Store blockcommit permissions...` due to unresolved concerns - Pass tapfd path through netdef instead of resolving from fd - Link to v1: https://lore.kernel.org/r/20260105-apparmor-races-v1-0-932cf0e990b7@canonica... --- src/conf/domain_conf.c | 8 ++++++++ src/conf/domain_conf.h | 1 + src/hypervisor/domain_interface.c | 2 +- src/lxc/lxc_process.c | 1 + src/qemu/qemu_interface.c | 1 + src/security/security_apparmor.c | 1 + src/security/virt-aa-helper.c | 5 +++++ src/util/virnetdevmacvlan.c | 18 +++++++++++------- src/util/virnetdevmacvlan.h | 4 +++- 9 files changed, 32 insertions(+), 9 deletions(-) diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index 02e23f78667a775637c710b651ba5fc7a127226f..1d7921e0de6f097ffaf86a9197d629e67dc213d7 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -2939,6 +2939,7 @@ virDomainNetDefFree(virDomainNetDef *def) g_free(def->virtio); g_free(def->coalesce); g_free(def->sourceDev); + g_free(def->tapfdpath); virNetDevIPInfoClear(&def->guestIP); virNetDevIPInfoClear(&def->hostIP); @@ -10440,6 +10441,10 @@ virDomainNetDefParseXML(virDomainXMLOption *xmlopt, return NULL; } + if (!(flags & VIR_DOMAIN_DEF_PARSE_INACTIVE)) { + def->tapfdpath = virXPathString("string(./tapfd/@path)", ctxt); + } + if (virNetworkPortOptionsParseXML(ctxt, &def->isolatedPort) < 0) return NULL; @@ -25664,6 +25669,9 @@ virDomainNetDefFormat(virBuffer *buf, if (def->mtu) virBufferAsprintf(buf, "<mtu size='%u'/>\n", def->mtu); + if (def->tapfdpath && (flags & VIR_DOMAIN_DEF_FORMAT_STATUS)) + virBufferAsprintf(buf, "<tapfd path='%s'/>\n", def->tapfdpath); + virDomainNetDefCoalesceFormatXML(buf, def->coalesce); virDomainDeviceInfoFormat(buf, &def->info, flags | VIR_DOMAIN_DEF_FORMAT_ALLOW_BOOT diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h index 66dc4e3417b8cb5bce60217a4e529add61149962..ba2bf1f750dcd7f4f25ef3bf55fd63629d3b5222 100644 --- a/src/conf/domain_conf.h +++ b/src/conf/domain_conf.h @@ -1203,6 +1203,7 @@ struct _virDomainNetDef { char *downscript; char *domain_name; /* backend domain name */ char *ifname; /* interface name on the host (<target dev='x'/>) */ + char *tapfdpath; /* Path in /dev for macvtap (<tapfd path="/dev/tapXX">) */ virTristateBool managed_tap; virNetDevIPInfo hostIP; char *ifname_guest_actual; diff --git a/src/hypervisor/domain_interface.c b/src/hypervisor/domain_interface.c index 5bc698d2727e1142e9c5dc30ac00975f268f98e8..37e3d453a03943ee5729ad2d4b087b5e0ca37408 100644 --- a/src/hypervisor/domain_interface.c +++ b/src/hypervisor/domain_interface.c @@ -111,7 +111,7 @@ virDomainInterfaceEthernetConnect(virDomainDef *def, if (virNetDevMacVLanIsMacvtap(net->ifname)) { auditdev = net->ifname; - if (virNetDevMacVLanTapOpen(net->ifname, tapfd, tapfdSize) < 0) + if (virNetDevMacVLanTapOpen(net->ifname, tapfd, tapfdSize, &net->tapfdpath) < 0) goto cleanup; if (virNetDevMacVLanTapSetup(tapfd, tapfdSize, virDomainInterfaceIsVnetCompatModel(net)) < 0) { diff --git a/src/lxc/lxc_process.c b/src/lxc/lxc_process.c index 1bca9e8daea2cb8f63bcf5c0a735252ff57af6f1..c731b28871b18329e633c42f2141d22063208d9f 100644 --- a/src/lxc/lxc_process.c +++ b/src/lxc/lxc_process.c @@ -379,6 +379,7 @@ virLXCProcessSetupInterfaceDirect(virLXCDriver *driver, VIR_NETDEV_VPORT_PROFILE_OP_CREATE, cfg->stateDir, NULL, 0, + &net->tapfdpath, macvlan_create_flags) < 0) return NULL; diff --git a/src/qemu/qemu_interface.c b/src/qemu/qemu_interface.c index 23a23d201aec31a36431646551ae03a233606e30..edc53d53b3b34afbfb8662e809bc0898076fdfc5 100644 --- a/src/qemu/qemu_interface.c +++ b/src/qemu/qemu_interface.c @@ -81,6 +81,7 @@ qemuInterfaceDirectConnect(virDomainDef *def, &res_ifname, vmop, cfg->stateDir, tapfd, tapfdSize, + &net->tapfdpath, macvlan_create_flags) < 0) goto cleanup; diff --git a/src/security/security_apparmor.c b/src/security/security_apparmor.c index 934acfb46198401d84d47cc6266a9403eda5a3b0..dec271721641c811944f98464cebebca6ed6a159 100644 --- a/src/security/security_apparmor.c +++ b/src/security/security_apparmor.c @@ -157,6 +157,7 @@ load_profile(virSecurityManager *mgr G_GNUC_UNUSED, if (virDomainDefFormatInternal(def, NULL, &buf, VIR_DOMAIN_DEF_FORMAT_SECURE | + VIR_DOMAIN_DEF_FORMAT_STATUS | VIR_DOMAIN_DEF_FORMAT_VOLUME_TRANSLATED) < 0) return -1; diff --git a/src/security/virt-aa-helper.c b/src/security/virt-aa-helper.c index f4ec6b7826ba532f0dbac2dcd4ed89f7f98e6be6..e904d5e8292ae5e7d4acbec2062a91861a9535f5 100644 --- a/src/security/virt-aa-helper.c +++ b/src/security/virt-aa-helper.c @@ -1176,6 +1176,11 @@ get_files(vahControl * ctl) vhu->type) != 0) return -1; } + + if (net->tapfdpath) { + if (vah_add_file(&buf, net->tapfdpath, "rwk") != 0) + return -1; + } } for (i = 0; i < ctl->def->nmems; i++) { diff --git a/src/util/virnetdevmacvlan.c b/src/util/virnetdevmacvlan.c index cde9d70eefd047dc5c16056f6697cf4d05bc0795..fcf63e08ff07eca22a122a2532cea1b0c9a95c9e 100644 --- a/src/util/virnetdevmacvlan.c +++ b/src/util/virnetdevmacvlan.c @@ -152,24 +152,24 @@ int virNetDevMacVLanDelete(const char *ifname) int virNetDevMacVLanTapOpen(const char *ifname, int *tapfd, - size_t tapfdSize) + size_t tapfdSize, + char **tapname) { int retries = 10; int ret = -1; int ifindex; size_t i = 0; - g_autofree char *tapname = NULL; if (virNetDevGetIndex(ifname, &ifindex) < 0) return -1; - tapname = g_strdup_printf("/dev/tap%d", ifindex); + *tapname = g_strdup_printf("/dev/tap%d", ifindex); for (i = 0; i < tapfdSize; i++) { int fd = -1; while (fd < 0) { - if ((fd = open(tapname, O_RDWR)) >= 0) { + if ((fd = open(*tapname, O_RDWR)) >= 0) { tapfd[i] = fd; } else if (retries-- > 0) { /* may need to wait for udev to be done */ @@ -178,7 +178,7 @@ virNetDevMacVLanTapOpen(const char *ifname, /* However, if haven't succeeded, quit. */ virReportSystemError(errno, _("cannot open macvtap tap device %1$s"), - tapname); + *tapname); goto cleanup; } } @@ -188,6 +188,7 @@ virNetDevMacVLanTapOpen(const char *ifname, cleanup: if (ret < 0) { + g_free(*tapname); while (i--) VIR_FORCE_CLOSE(tapfd[i]); } @@ -659,6 +660,7 @@ virNetDevMacVLanCreateWithVPortProfile(const char *ifnameRequested, char *stateDir, int *tapfd, size_t tapfdSize, + char **tapfdpath, unsigned int flags) { g_autofree char *ifname = NULL; @@ -729,7 +731,7 @@ virNetDevMacVLanCreateWithVPortProfile(const char *ifnameRequested, } if (flags & VIR_NETDEV_MACVLAN_CREATE_WITH_TAP) { - if (virNetDevMacVLanTapOpen(ifname, tapfd, tapfdSize) < 0) + if (virNetDevMacVLanTapOpen(ifname, tapfd, tapfdSize, tapfdpath) < 0) goto disassociate_exit; if (virNetDevMacVLanTapSetup(tapfd, tapfdSize, vnet_hdr) < 0) @@ -888,7 +890,8 @@ int virNetDevMacVLanDelete(const char *ifname G_GNUC_UNUSED) int virNetDevMacVLanTapOpen(const char *ifname G_GNUC_UNUSED, int *tapfd G_GNUC_UNUSED, - size_t tapfdSize G_GNUC_UNUSED) + size_t tapfdSize G_GNUC_UNUSED, + char **tapname G_GNUC_UNUSED) { virReportSystemError(ENOSYS, "%s", _("Cannot create macvlan devices on this platform")); @@ -917,6 +920,7 @@ int virNetDevMacVLanCreateWithVPortProfile(const char *ifname G_GNUC_UNUSED, char *stateDir G_GNUC_UNUSED, int *tapfd G_GNUC_UNUSED, size_t tapfdSize G_GNUC_UNUSED, + char **tapfdpath G_GNUC_UNUSED, unsigned int unused_flags G_GNUC_UNUSED) { virReportSystemError(ENOSYS, "%s", diff --git a/src/util/virnetdevmacvlan.h b/src/util/virnetdevmacvlan.h index 31e4804cdc0d7c4beb74ba66d204d0ff7ad83151..7424b8796529d6c6d1909eee81c88e8ded0ea84b 100644 --- a/src/util/virnetdevmacvlan.h +++ b/src/util/virnetdevmacvlan.h @@ -72,13 +72,15 @@ int virNetDevMacVLanCreateWithVPortProfile(const char *ifname, char *stateDir, int *tapfd, size_t tapfdSize, + char **tapfdpath, unsigned int flags) ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(3) ATTRIBUTE_NONNULL(6) ATTRIBUTE_NONNULL(8) ATTRIBUTE_NONNULL(10) G_GNUC_WARN_UNUSED_RESULT; int virNetDevMacVLanTapOpen(const char *ifname, int *tapfd, - size_t tapfdSize) + size_t tapfdSize, + char **tapname) ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) G_GNUC_WARN_UNUSED_RESULT; --- base-commit: 74fc02d792f7ee55d2e0a7b9ad4e6d751c36ceb8 change-id: 20260105-apparmor-races-d03238ee4d93 Best regards, -- Wesley Hershberger <wesley.hershberger@canonical.com>