[PATCH 2/2] qemu: Tell secdrivers which images are top parent

When preparing images for block jobs we modify their seclabels so that QEMU can open them. However, as mentioned in the previous commit, secdrivers base some it their decisions whether the image they are working on is top parent or not. Fortunately, in places where we call secdrivers we know this and the information can be passed to secdrivers. This fixes the problem described in the linked bugzilla. The problem is the following: after the first blockcommit from the base to one of the parents the XATTRs on the base image are not cleared and therefore the second attempt to do another blockcommit fails. This is caused by blockcommit code calling qemuSecuritySetImageLabel() over the base image and never calling the corresponding qemuSecurityRestoreImageLabel(). A naive fix would be to call the restore function. But this is not possible, because that would deny QEMU the access to the base image. Fortunately, we can use the fact that seclabels are remembered only for the top parent and not for the rest of the backing chain. And thanks to the previous commit we can tell secdrivers which images are top parents. Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1803551 Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- src/qemu/qemu_backup.c | 4 ++-- src/qemu/qemu_blockjob.c | 6 ++++-- src/qemu/qemu_checkpoint.c | 6 ++++-- src/qemu/qemu_domain.c | 15 +++++++++++++-- src/qemu/qemu_domain.h | 3 ++- src/qemu/qemu_driver.c | 15 ++++++++++----- src/qemu/qemu_process.c | 2 +- src/qemu/qemu_security.c | 6 +++++- src/qemu/qemu_security.h | 3 ++- 9 files changed, 43 insertions(+), 17 deletions(-) diff --git a/src/qemu/qemu_backup.c b/src/qemu/qemu_backup.c index 2cc6ff7a42..8b66ee8d1f 100644 --- a/src/qemu/qemu_backup.c +++ b/src/qemu/qemu_backup.c @@ -469,8 +469,8 @@ qemuBackupDiskPrepareOneStorage(virDomainObjPtr vm, dd->created = true; } - if (qemuDomainStorageSourceAccessAllow(priv->driver, vm, dd->store, false, - true) < 0) + if (qemuDomainStorageSourceAccessAllow(priv->driver, vm, dd->store, + false, true, true) < 0) return -1; dd->labelled = true; diff --git a/src/qemu/qemu_blockjob.c b/src/qemu/qemu_blockjob.c index 71df0d1ab2..9db1b71a3e 100644 --- a/src/qemu/qemu_blockjob.c +++ b/src/qemu/qemu_blockjob.c @@ -1105,9 +1105,11 @@ qemuBlockJobProcessEventCompletedCommit(virQEMUDriverPtr driver, return; /* revert access to images */ - qemuDomainStorageSourceAccessAllow(driver, vm, job->data.commit.base, true, false); + qemuDomainStorageSourceAccessAllow(driver, vm, job->data.commit.base, + true, false, false); if (job->data.commit.topparent != job->disk->src) - qemuDomainStorageSourceAccessAllow(driver, vm, job->data.commit.topparent, true, false); + qemuDomainStorageSourceAccessAllow(driver, vm, job->data.commit.topparent, + true, false, false); baseparent->backingStore = NULL; job->data.commit.topparent->backingStore = job->data.commit.base; diff --git a/src/qemu/qemu_checkpoint.c b/src/qemu/qemu_checkpoint.c index c06bfe6a21..fe54af74ec 100644 --- a/src/qemu/qemu_checkpoint.c +++ b/src/qemu/qemu_checkpoint.c @@ -298,7 +298,8 @@ qemuCheckpointDiscardBitmaps(virDomainObjPtr vm, for (next = reopenimages; next; next = next->next) { virStorageSourcePtr src = next->data; - if (qemuDomainStorageSourceAccessAllow(driver, vm, src, false, false) < 0) + if (qemuDomainStorageSourceAccessAllow(driver, vm, src, + false, false, false) < 0) goto relabel; relabelimages = g_slist_prepend(relabelimages, src); @@ -313,7 +314,8 @@ qemuCheckpointDiscardBitmaps(virDomainObjPtr vm, for (next = relabelimages; next; next = next->next) { virStorageSourcePtr src = next->data; - ignore_value(qemuDomainStorageSourceAccessAllow(driver, vm, src, true, false)); + ignore_value(qemuDomainStorageSourceAccessAllow(driver, vm, src, + true, false, false)); } return rc; diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c index 3dfa71650d..32e8220d98 100644 --- a/src/qemu/qemu_domain.c +++ b/src/qemu/qemu_domain.c @@ -11589,6 +11589,8 @@ typedef enum { QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_SKIP_REVOKE = 1 << 4, /* VM already has access to the source and we are just modifying it */ QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_MODIFY_ACCESS = 1 << 5, + /* whether the image is top parent of backing chain */ + QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_TOP_PARENT = 1 << 6, } qemuDomainStorageSourceAccessFlags; @@ -11666,6 +11668,7 @@ qemuDomainStorageSourceAccessModify(virQEMUDriverPtr driver, bool force_ro = flags & QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_FORCE_READ_ONLY; bool force_rw = flags & QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_FORCE_READ_WRITE; bool revoke = flags & QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_REVOKE; + bool topparent = flags & QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_TOP_PARENT; int rc; bool was_readonly = src->readonly; bool revoke_cgroup = false; @@ -11712,7 +11715,7 @@ qemuDomainStorageSourceAccessModify(virQEMUDriverPtr driver, revoke_namespace = true; } - if (qemuSecuritySetImageLabel(driver, vm, src, chain) < 0) + if (qemuSecuritySetImageLabel(driver, vm, src, chain, topparent) < 0) goto revoke; revoke_label = true; @@ -11817,6 +11820,7 @@ qemuDomainStorageSourceAccessRevoke(virQEMUDriverPtr driver, * @elem: source structure to set access for * @readonly: setup read-only access if true * @newSource: @elem describes a storage source which @vm can't access yet + * @topparent: @elem is top parent of backing chain * * Allow a VM access to a single element of a disk backing chain; this helper * ensures that the lock manager, cgroup device controller, and security manager @@ -11824,13 +11828,17 @@ qemuDomainStorageSourceAccessRevoke(virQEMUDriverPtr driver, * * When modifying permissions of @elem which @vm can already access (is in the * backing chain) @newSource needs to be set to false. + * + * When the @elem is top parent of a backing chain, then @topparent must be + * true, otherwise it must be false. */ int qemuDomainStorageSourceAccessAllow(virQEMUDriverPtr driver, virDomainObjPtr vm, virStorageSourcePtr elem, bool readonly, - bool newSource) + bool newSource, + bool topparent) { qemuDomainStorageSourceAccessFlags flags = QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_SKIP_REVOKE; @@ -11842,6 +11850,9 @@ qemuDomainStorageSourceAccessAllow(virQEMUDriverPtr driver, if (!newSource) flags |= QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_MODIFY_ACCESS; + if (topparent) + flags |= QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_TOP_PARENT; + return qemuDomainStorageSourceAccessModify(driver, vm, elem, flags); } diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h index f8fb48f2ff..f679cdbf09 100644 --- a/src/qemu/qemu_domain.h +++ b/src/qemu/qemu_domain.h @@ -896,7 +896,8 @@ int qemuDomainStorageSourceAccessAllow(virQEMUDriverPtr driver, virDomainObjPtr vm, virStorageSourcePtr elem, bool readonly, - bool newSource); + bool newSource, + bool topparent); int qemuDomainPrepareStorageSourceBlockdev(virDomainDiskDefPtr disk, virStorageSourcePtr src, diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 35ade1ef37..39c29a0d47 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -15141,7 +15141,8 @@ qemuDomainSnapshotDiskPrepareOne(virQEMUDriverPtr driver, } /* set correct security, cgroup and locking options on the new image */ - if (qemuDomainStorageSourceAccessAllow(driver, vm, dd->src, false, true) < 0) + if (qemuDomainStorageSourceAccessAllow(driver, vm, dd->src, + false, true, true) < 0) return -1; dd->prepared = true; @@ -18489,9 +18490,11 @@ qemuDomainBlockCommit(virDomainPtr dom, * operation succeeds, but doing that requires tracking the * operation in XML across libvirtd restarts. */ clean_access = true; - if (qemuDomainStorageSourceAccessAllow(driver, vm, baseSource, false, false) < 0 || + if (qemuDomainStorageSourceAccessAllow(driver, vm, baseSource, + false, false, false) < 0 || (top_parent && top_parent != disk->src && - qemuDomainStorageSourceAccessAllow(driver, vm, top_parent, false, false) < 0)) + qemuDomainStorageSourceAccessAllow(driver, vm, top_parent, + false, false, false) < 0)) goto endjob; if (!(job = qemuBlockJobDiskNewCommit(vm, disk, top_parent, topSource, @@ -18551,9 +18554,11 @@ qemuDomainBlockCommit(virDomainPtr dom, virErrorPtr orig_err; virErrorPreserveLast(&orig_err); /* Revert access to read-only, if possible. */ - qemuDomainStorageSourceAccessAllow(driver, vm, baseSource, true, false); + qemuDomainStorageSourceAccessAllow(driver, vm, baseSource, + true, false, false); if (top_parent && top_parent != disk->src) - qemuDomainStorageSourceAccessAllow(driver, vm, top_parent, true, false); + qemuDomainStorageSourceAccessAllow(driver, vm, top_parent, + true, false, false); virErrorRestore(&orig_err); } diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c index d9035055e8..425a21d77e 100644 --- a/src/qemu/qemu_process.c +++ b/src/qemu/qemu_process.c @@ -7851,7 +7851,7 @@ qemuProcessRefreshLegacyBlockjob(void *payload, (qemuDomainNamespaceSetupDisk(vm, disk->mirror) < 0 || qemuSetupImageChainCgroup(vm, disk->mirror) < 0 || qemuSecuritySetImageLabel(priv->driver, vm, disk->mirror, - true) < 0)) + true, false) < 0)) goto cleanup; } } diff --git a/src/qemu/qemu_security.c b/src/qemu/qemu_security.c index 2aa2b5b9c6..ad9d0b8012 100644 --- a/src/qemu/qemu_security.c +++ b/src/qemu/qemu_security.c @@ -98,7 +98,8 @@ int qemuSecuritySetImageLabel(virQEMUDriverPtr driver, virDomainObjPtr vm, virStorageSourcePtr src, - bool backingChain) + bool backingChain, + bool topparent) { qemuDomainObjPrivatePtr priv = vm->privateData; pid_t pid = -1; @@ -108,6 +109,9 @@ qemuSecuritySetImageLabel(virQEMUDriverPtr driver, if (backingChain) labelFlags |= VIR_SECURITY_DOMAIN_IMAGE_LABEL_BACKING_CHAIN; + if (topparent) + labelFlags |= VIR_SECURITY_DOMAIN_IMAGE_TOP_PARENT; + if (qemuDomainNamespaceEnabled(vm, QEMU_DOMAIN_NS_MOUNT)) pid = vm->pid; diff --git a/src/qemu/qemu_security.h b/src/qemu/qemu_security.h index a8c648ece1..90ff660257 100644 --- a/src/qemu/qemu_security.h +++ b/src/qemu/qemu_security.h @@ -36,7 +36,8 @@ void qemuSecurityRestoreAllLabel(virQEMUDriverPtr driver, int qemuSecuritySetImageLabel(virQEMUDriverPtr driver, virDomainObjPtr vm, virStorageSourcePtr src, - bool backingChain); + bool backingChain, + bool topparent); int qemuSecurityRestoreImageLabel(virQEMUDriverPtr driver, virDomainObjPtr vm, -- 2.24.1