[PATCH v2 0/2] security: Handle non top most parents better
v2 of: https://www.redhat.com/archives/libvir-list/2020-February/msg01113.html diff to v2: - fixed wording/naming - fixed passing true/false in cases identified by Peter Michal Prívozník (2): security: Introduce VIR_SECURITY_DOMAIN_IMAGE_PARENT_CHAIN_TOP flag qemu: Tell secdrivers which images are top parent src/qemu/qemu_backup.c | 4 ++-- src/qemu/qemu_blockjob.c | 6 ++++-- src/qemu/qemu_checkpoint.c | 6 ++++-- src/qemu/qemu_domain.c | 24 ++++++++++++++++++++---- src/qemu/qemu_domain.h | 3 ++- src/qemu/qemu_driver.c | 23 +++++++++++++++++------ src/qemu/qemu_process.c | 2 +- src/qemu/qemu_security.c | 6 +++++- src/qemu/qemu_security.h | 3 ++- src/security/security_dac.c | 15 ++++++++++----- src/security/security_manager.h | 4 ++++ src/security/security_selinux.c | 17 +++++++++++------ 12 files changed, 82 insertions(+), 31 deletions(-) -- 2.24.1
Our decision whether to remember seclabel for a disk image depends on a few factors. If the image is readonly or shared or not the chain top the remembering is suppressed for the image. However, the virSecurityManagerSetImageLabel() is too low level to determine whether passed @src is chain top or not. Even though the function has the @parent argument it does not necessarily reflect the chain top - it only points to the top level image in the chain we want to relabel and not to the topmost image of the whole chain. And this can't be derived from the passed domain definition reliably neither - in some cases (like snapshots or block copy) the @src is added to the definition only after the operation succeeded. Therefore, introduce a flag which callers can use to help us with the decision. Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- src/security/security_dac.c | 15 ++++++++++----- src/security/security_manager.h | 4 ++++ src/security/security_selinux.c | 17 +++++++++++------ 3 files changed, 25 insertions(+), 11 deletions(-) diff --git a/src/security/security_dac.c b/src/security/security_dac.c index f412054d0e..34da07fc9f 100644 --- a/src/security/security_dac.c +++ b/src/security/security_dac.c @@ -889,14 +889,14 @@ static int virSecurityDACSetImageLabelInternal(virSecurityManagerPtr mgr, virDomainDefPtr def, virStorageSourcePtr src, - virStorageSourcePtr parent) + virStorageSourcePtr parent, + bool is_topparent) { virSecurityLabelDefPtr secdef; virSecurityDeviceLabelDefPtr disk_seclabel; virSecurityDeviceLabelDefPtr parent_seclabel = NULL; virSecurityDACDataPtr priv = virSecurityManagerGetPrivateData(mgr); bool remember; - bool is_toplevel = parent == src || parent->externalDataStore == src; uid_t user; gid_t group; @@ -954,7 +954,7 @@ virSecurityDACSetImageLabelInternal(virSecurityManagerPtr mgr, * but the top layer, or read only image, or disk explicitly * marked as shared. */ - remember = is_toplevel && !src->readonly && !src->shared; + remember = is_topparent && !src->readonly && !src->shared; return virSecurityDACSetOwnership(mgr, src, NULL, user, group, remember); } @@ -970,7 +970,9 @@ virSecurityDACSetImageLabelRelative(virSecurityManagerPtr mgr, virStorageSourcePtr n; for (n = src; virStorageSourceIsBacking(n); n = n->backingStore) { - if (virSecurityDACSetImageLabelInternal(mgr, def, n, parent) < 0) + const bool is_topparent = flags & VIR_SECURITY_DOMAIN_IMAGE_PARENT_CHAIN_TOP; + + if (virSecurityDACSetImageLabelInternal(mgr, def, n, parent, is_topparent) < 0) return -1; if (n->externalDataStore && @@ -983,6 +985,8 @@ virSecurityDACSetImageLabelRelative(virSecurityManagerPtr mgr, if (!(flags & VIR_SECURITY_DOMAIN_IMAGE_LABEL_BACKING_CHAIN)) break; + + flags &= ~VIR_SECURITY_DOMAIN_IMAGE_PARENT_CHAIN_TOP; } return 0; @@ -2114,7 +2118,8 @@ virSecurityDACSetAllLabel(virSecurityManagerPtr mgr, if (virDomainDiskGetType(def->disks[i]) == VIR_STORAGE_TYPE_DIR) continue; if (virSecurityDACSetImageLabel(mgr, def, def->disks[i]->src, - VIR_SECURITY_DOMAIN_IMAGE_LABEL_BACKING_CHAIN) < 0) + VIR_SECURITY_DOMAIN_IMAGE_LABEL_BACKING_CHAIN | + VIR_SECURITY_DOMAIN_IMAGE_PARENT_CHAIN_TOP) < 0) return -1; } diff --git a/src/security/security_manager.h b/src/security/security_manager.h index b92ea5dc87..7699bcbc6f 100644 --- a/src/security/security_manager.h +++ b/src/security/security_manager.h @@ -151,6 +151,10 @@ virSecurityManagerPtr* virSecurityManagerGetNested(virSecurityManagerPtr mgr); typedef enum { VIR_SECURITY_DOMAIN_IMAGE_LABEL_BACKING_CHAIN = 1 << 0, + /* The VIR_SECURITY_DOMAIN_IMAGE_PARENT_CHAIN_TOP should be set if the + * image passed to virSecurityManagerSetImageLabel() is the top parent of + * the whole backing chain. */ + VIR_SECURITY_DOMAIN_IMAGE_PARENT_CHAIN_TOP = 1 << 1, } virSecurityDomainImageLabelFlags; int virSecurityManagerSetImageLabel(virSecurityManagerPtr mgr, diff --git a/src/security/security_selinux.c b/src/security/security_selinux.c index 2241a35e6e..90b992d1e1 100644 --- a/src/security/security_selinux.c +++ b/src/security/security_selinux.c @@ -1824,7 +1824,8 @@ static int virSecuritySELinuxSetImageLabelInternal(virSecurityManagerPtr mgr, virDomainDefPtr def, virStorageSourcePtr src, - virStorageSourcePtr parent) + virStorageSourcePtr parent, + bool is_topparent) { virSecuritySELinuxDataPtr data = virSecurityManagerGetPrivateData(mgr); virSecurityLabelDefPtr secdef; @@ -1832,7 +1833,6 @@ virSecuritySELinuxSetImageLabelInternal(virSecurityManagerPtr mgr, virSecurityDeviceLabelDefPtr parent_seclabel = NULL; char *use_label = NULL; bool remember; - bool is_toplevel = parent == src || parent->externalDataStore == src; g_autofree char *vfioGroupDev = NULL; const char *path = src->path; int ret; @@ -1856,7 +1856,7 @@ virSecuritySELinuxSetImageLabelInternal(virSecurityManagerPtr mgr, * but the top layer, or read only image, or disk explicitly * marked as shared. */ - remember = is_toplevel && !src->readonly && !src->shared; + remember = is_topparent && !src->readonly && !src->shared; disk_seclabel = virStorageSourceGetSecurityLabelDef(src, SECURITY_SELINUX_NAME); @@ -1873,7 +1873,7 @@ virSecuritySELinuxSetImageLabelInternal(virSecurityManagerPtr mgr, return 0; use_label = parent_seclabel->label; - } else if (is_toplevel) { + } else if (parent == src || parent->externalDataStore == src) { if (src->shared) { use_label = data->file_context; } else if (src->readonly) { @@ -1930,7 +1930,9 @@ virSecuritySELinuxSetImageLabelRelative(virSecurityManagerPtr mgr, virStorageSourcePtr n; for (n = src; virStorageSourceIsBacking(n); n = n->backingStore) { - if (virSecuritySELinuxSetImageLabelInternal(mgr, def, n, parent) < 0) + const bool is_topparent = flags & VIR_SECURITY_DOMAIN_IMAGE_PARENT_CHAIN_TOP; + + if (virSecuritySELinuxSetImageLabelInternal(mgr, def, n, parent, is_topparent) < 0) return -1; if (n->externalDataStore && @@ -1943,6 +1945,8 @@ virSecuritySELinuxSetImageLabelRelative(virSecurityManagerPtr mgr, if (!(flags & VIR_SECURITY_DOMAIN_IMAGE_LABEL_BACKING_CHAIN)) break; + + flags &= ~VIR_SECURITY_DOMAIN_IMAGE_PARENT_CHAIN_TOP; } return 0; @@ -3146,7 +3150,8 @@ virSecuritySELinuxSetAllLabel(virSecurityManagerPtr mgr, continue; } if (virSecuritySELinuxSetImageLabel(mgr, def, def->disks[i]->src, - VIR_SECURITY_DOMAIN_IMAGE_LABEL_BACKING_CHAIN) < 0) + VIR_SECURITY_DOMAIN_IMAGE_LABEL_BACKING_CHAIN | + VIR_SECURITY_DOMAIN_IMAGE_PARENT_CHAIN_TOP) < 0) return -1; } /* XXX fixme process def->fss if relabel == true */ -- 2.24.1
On Mon, Mar 09, 2020 at 09:29:42 +0100, Michal Privoznik wrote:
Our decision whether to remember seclabel for a disk image depends on a few factors. If the image is readonly or shared or not the chain top the remembering is suppressed for the image. However, the virSecurityManagerSetImageLabel() is too low level to determine whether passed @src is chain top or not. Even though the function has the @parent argument it does not necessarily reflect the chain top - it only points to the top level image in the chain we want to relabel and not to the topmost image of the whole chain. And this can't be derived from the passed domain definition reliably neither - in some cases (like snapshots or block copy) the @src is added to the definition only after the operation succeeded. Therefore, introduce a flag which callers can use to help us with the decision.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- src/security/security_dac.c | 15 ++++++++++----- src/security/security_manager.h | 4 ++++ src/security/security_selinux.c | 17 +++++++++++------ 3 files changed, 25 insertions(+), 11 deletions(-)
diff --git a/src/security/security_dac.c b/src/security/security_dac.c index f412054d0e..34da07fc9f 100644 --- a/src/security/security_dac.c +++ b/src/security/security_dac.c @@ -889,14 +889,14 @@ static int virSecurityDACSetImageLabelInternal(virSecurityManagerPtr mgr, virDomainDefPtr def, virStorageSourcePtr src, - virStorageSourcePtr parent) + virStorageSourcePtr parent, + bool is_topparent)
The variable name is still confusing. Since it's the point of first contact with the code, you should change that one as well. I'm sorry I didn't point this out explicitly in my previous review, but I wanted both the flag name and the variable names changed. Especially since they are the same except for being lowercase. Also please fix all the functions, not just this one.
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 of of the backing chain. Fortunately, in places where we call secdrivers we know this and the information can be passed to secdrivers. 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, possibly multiple times (to ensure RW/RO access). 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 of the backing chain and not for the rest of the backing chain. And thanks to the previous commit we can tell secdrivers which images are top of the backing chain. Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1803551 Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- src/qemu/qemu_backup.c | 4 ++-- src/qemu/qemu_blockjob.c | 6 ++++-- src/qemu/qemu_checkpoint.c | 6 ++++-- src/qemu/qemu_domain.c | 24 ++++++++++++++++++++---- src/qemu/qemu_domain.h | 3 ++- src/qemu/qemu_driver.c | 23 +++++++++++++++++------ src/qemu/qemu_process.c | 2 +- src/qemu/qemu_security.c | 6 +++++- src/qemu/qemu_security.h | 3 ++- 9 files changed, 57 insertions(+), 20 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..e894e1634d 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, true); 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 a387e7dfe7..ea87b09aa0 100644 --- a/src/qemu/qemu_checkpoint.c +++ b/src/qemu/qemu_checkpoint.c @@ -296,7 +296,8 @@ 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); @@ -311,7 +312,8 @@ 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 33c2158eb5..5b53d74d38 100644 --- a/src/qemu/qemu_domain.c +++ b/src/qemu/qemu_domain.c @@ -11668,6 +11668,8 @@ 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 the top image of the backing chain (e.g. disk source) */ + QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_CHAIN_TOP = 1 << 6, } qemuDomainStorageSourceAccessFlags; @@ -11745,6 +11747,7 @@ 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_CHAIN_TOP; int rc; bool was_readonly = src->readonly; bool revoke_cgroup = false; @@ -11791,7 +11794,7 @@ 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; @@ -11854,7 +11857,8 @@ qemuDomainStorageSourceChainAccessAllow(virQEMUDriverPtr driver, virDomainObjPtr vm, virStorageSourcePtr src) { - qemuDomainStorageSourceAccessFlags flags = QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_CHAIN; + qemuDomainStorageSourceAccessFlags flags = QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_CHAIN | + QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_CHAIN_TOP; return qemuDomainStorageSourceAccessModify(driver, vm, src, flags); } @@ -11866,7 +11870,8 @@ qemuDomainStorageSourceChainAccessRevoke(virQEMUDriverPtr driver, virStorageSourcePtr src) { qemuDomainStorageSourceAccessFlags flags = QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_REVOKE | - QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_CHAIN; + QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_CHAIN | + QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_CHAIN_TOP; return qemuDomainStorageSourceAccessModify(driver, vm, src, flags); } @@ -11896,6 +11901,7 @@ 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 @@ -11903,13 +11909,20 @@ 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. + * + * The @topparent flag must be set if the @elem image is the topmost image of a + * given backing chain or meant to become the topmost image (for e.g. + * snapshots, or blockcopy or even in the end for active layer block commit, + * where we discard the top of the backing chain so one of the intermediates + * (the base) becomes the top of the chain). */ 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; @@ -11921,6 +11934,9 @@ qemuDomainStorageSourceAccessAllow(virQEMUDriverPtr driver, if (!newSource) flags |= QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_MODIFY_ACCESS; + if (topparent) + flags |= QEMU_DOMAIN_STORAGE_SOURCE_ACCESS_CHAIN_TOP; + return qemuDomainStorageSourceAccessModify(driver, vm, elem, flags); } diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h index 476056c73f..8c031abf82 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 3707448f49..b392ba25a6 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -15142,7 +15142,8 @@ 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; @@ -18490,11 +18491,19 @@ 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 || - (top_parent && top_parent != disk->src && - qemuDomainStorageSourceAccessAllow(driver, vm, top_parent, false, false) < 0)) + if (qemuDomainStorageSourceAccessAllow(driver, vm, baseSource, + false, false, false) < 0) goto endjob; + if (top_parent && top_parent != disk->src) { + /* While top_parent is topmost image, we don't need to remember its + * owner as it will be overwritten upon finishing the commit. Hence, + * pass topparent = false. */ + if (qemuDomainStorageSourceAccessAllow(driver, vm, top_parent, + false, false, false) < 0) + goto endjob; + } + if (!(job = qemuBlockJobDiskNewCommit(vm, disk, top_parent, topSource, baseSource, flags & VIR_DOMAIN_BLOCK_COMMIT_DELETE, @@ -18552,9 +18561,11 @@ 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 bec822a2ae..499d39a920 100644 --- a/src/qemu/qemu_process.c +++ b/src/qemu/qemu_process.c @@ -7856,7 +7856,7 @@ qemuProcessRefreshLegacyBlockjob(void *payload, (qemuDomainNamespaceSetupDisk(vm, disk->mirror) < 0 || qemuSetupImageChainCgroup(vm, disk->mirror) < 0 || qemuSecuritySetImageLabel(priv->driver, vm, disk->mirror, - true) < 0)) + true, true) < 0)) goto cleanup; } } diff --git a/src/qemu/qemu_security.c b/src/qemu/qemu_security.c index 2aa2b5b9c6..8660f70305 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_PARENT_CHAIN_TOP; + 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
On Mon, Mar 09, 2020 at 09:29:43 +0100, Michal Privoznik wrote:
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 of of the backing chain. Fortunately, in places where we call secdrivers we know this and the information can be passed to secdrivers.
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, possibly multiple times (to ensure RW/RO access). 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 of the backing chain and not for the rest of the backing chain. And thanks to the previous commit we can tell secdrivers which images are top of the backing chain.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1803551
Signed-off-by: Michal Privoznik <mprivozn@redhat.com> ---
Once you fix all of the wrong variable name in this patch as well as in the previous one: Reviewed-by: Peter Krempa <pkrempa@redhat.com> On both.
On 3/9/20 10:18 AM, Peter Krempa wrote:
On Mon, Mar 09, 2020 at 09:29:43 +0100, Michal Privoznik wrote:
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 of of the backing chain. Fortunately, in places where we call secdrivers we know this and the information can be passed to secdrivers.
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, possibly multiple times (to ensure RW/RO access). 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 of the backing chain and not for the rest of the backing chain. And thanks to the previous commit we can tell secdrivers which images are top of the backing chain.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1803551
Signed-off-by: Michal Privoznik <mprivozn@redhat.com> ---
Once you fix all of the wrong variable name in this patch as well as in the previous one:
Does isParentChainTop sound good for the variable name? Michal
On Mon, Mar 09, 2020 at 13:39:56 +0100, Michal Privoznik wrote:
On 3/9/20 10:18 AM, Peter Krempa wrote:
On Mon, Mar 09, 2020 at 09:29:43 +0100, Michal Privoznik wrote:
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 of of the backing chain. Fortunately, in places where we call secdrivers we know this and the information can be passed to secdrivers.
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, possibly multiple times (to ensure RW/RO access). 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 of the backing chain and not for the rest of the backing chain. And thanks to the previous commit we can tell secdrivers which images are top of the backing chain.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1803551
Signed-off-by: Michal Privoznik <mprivozn@redhat.com> ---
Once you fix all of the wrong variable name in this patch as well as in the previous one:
Does isParentChainTop sound good for the variable name?
IMO isChainTop should be enough.
participants (2)
-
Michal Privoznik -
Peter Krempa