[libvirt] [PATCH v3] qemu: Pass file descriptor when using TPM passthrough
Stefan Berger
stefanb at linux.vnet.ibm.com
Thu Nov 20 15:08:48 UTC 2014
Pass the TPM file descriptor to QEMU via command line.
Instead of passing /dev/tpm0 we now pass /dev/fdset/10 and the additional
parameters -add-fd set=10,fd=20.
This addresses the use case when QEMU is started with non-root privileges
and QEMU cannot open /dev/tpm0 for example.
One problem is that for the passing of the file descriptor set to work,
virCommandReorderFDs must not be called on the virCommand. This is prevented
by setting a flag in the virCommandPassFDGetFDIndex that is checked to be
clear when virCommandReorderFDs is run.
Signed-off-by: Stefan Berger <stefanb at linux.vnet.ibm.com>
v2->v3: Fixed some memory leaks
---
src/libvirt_private.syms | 1 +
src/qemu/qemu_command.c | 136 ++++++++++++++++++++++++++++++++++++++++++++---
src/util/vircommand.c | 33 ++++++++++++
src/util/vircommand.h | 3 ++
4 files changed, 166 insertions(+), 7 deletions(-)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index aeec440..3194e8b 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1164,6 +1164,7 @@ virCommandNewArgList;
virCommandNewArgs;
virCommandNonblockingFDs;
virCommandPassFD;
+virCommandPassFDGetFDIndex;
virCommandPassListenFDs;
virCommandRawStatus;
virCommandRequireHandshake;
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 8ed7934..17debba 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -159,6 +159,58 @@ VIR_ENUM_IMPL(qemuNumaPolicy, VIR_DOMAIN_NUMATUNE_MEM_LAST,
"interleave");
/**
+ * qemuVirCommandGetFDSet:
+ * @cmd: the command to modify
+ * @fd: fd to reassign to the child
+ *
+ * Get the parameters for the QEMU -add-fd command line option
+ * for the given file descriptor. The file descriptor must previously
+ * have been 'transferred' in a virCommandPassFD() call.
+ * This function for example returns "set=10,fd=20".
+ */
+static char *
+qemuVirCommandGetFDSet(virCommandPtr cmd, int fd)
+{
+ char *result = NULL;
+ int idx = virCommandPassFDGetFDIndex(cmd, fd);
+
+ if (idx >= 0) {
+ ignore_value(virAsprintf(&result, "set=%d,fd=%d", idx, fd) < 0);
+ } else {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("file descriptor %d has not been transferred"), fd);
+ }
+
+ return result;
+}
+
+/**
+ * qemuVirCommandGetDevSet:
+ * @cmd: the command to modify
+ * @fd: fd to reassign to the child
+ *
+ * Get the parameters for the QEMU path= parameter where a file
+ * descriptor is accessed via a file descriptor set, for example
+ * /dev/fdset/10. The file descriptor must previously have been
+ * 'transferred' in a virCommandPassFD() call.
+ */
+static char *
+qemuVirCommandGetDevSet(virCommandPtr cmd, int fd)
+{
+ char *result = NULL;
+ int idx = virCommandPassFDGetFDIndex(cmd, fd);
+
+ if (idx >= 0) {
+ ignore_value(virAsprintf(&result, "/dev/fdset/%d", idx) < 0);
+ } else {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("file descriptor %d has not been transferred"), fd);
+ }
+ return result;
+}
+
+
+/**
* qemuPhysIfaceConnect:
* @def: the definition of the VM (needed by 802.1Qbh and audit)
* @driver: pointer to the driver instance
@@ -5926,14 +5978,20 @@ qemuBuildRNGDeviceArgs(virCommandPtr cmd,
static char *qemuBuildTPMBackendStr(const virDomainDef *def,
+ virCommandPtr cmd,
virQEMUCapsPtr qemuCaps,
- const char *emulator)
+ const char *emulator,
+ int *tpmfd, int *cancelfd)
{
const virDomainTPMDef *tpm = def->tpm;
virBuffer buf = VIR_BUFFER_INITIALIZER;
const char *type = virDomainTPMBackendTypeToString(tpm->type);
- char *cancel_path;
+ char *cancel_path = NULL;
const char *tpmdev;
+ char *devset = NULL, *cancel_devset = NULL;
+
+ *tpmfd = -1;
+ *cancelfd = -1;
virBufferAsprintf(&buf, "%s,id=tpm-%s", type, tpm->info.alias);
@@ -5946,11 +6004,49 @@ static char *qemuBuildTPMBackendStr(const virDomainDef *def,
if (!(cancel_path = virTPMCreateCancelPath(tpmdev)))
goto error;
- virBufferAddLit(&buf, ",path=");
- virBufferEscape(&buf, ',', ",", "%s", tpmdev);
+ if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_ADD_FD)) {
+ *tpmfd = open(tpmdev, O_RDWR);
+ if (*tpmfd < 0) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("Could not open TPM device %s"), tpmdev);
+ goto error;
+ }
+
+ virCommandPassFD(cmd, *tpmfd,
+ VIR_COMMAND_PASS_FD_CLOSE_PARENT);
+ devset = qemuVirCommandGetDevSet(cmd, *tpmfd);
+ if (devset == NULL)
+ goto error;
+
+ *cancelfd = open(cancel_path, O_WRONLY);
+ if (*cancelfd < 0) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("Could not open TPM device's cancel path "
+ "%s"), cancel_path);
+ goto error;
+ }
+
+ virCommandPassFD(cmd, *cancelfd,
+ VIR_COMMAND_PASS_FD_CLOSE_PARENT);
+ cancel_devset = qemuVirCommandGetDevSet(cmd, *cancelfd);
+ if (cancel_devset == NULL)
+ goto error;
+
+ virBufferAddLit(&buf, ",path=");
+ virBufferEscape(&buf, ',', ",", "%s", devset);
+ VIR_FREE(devset);
- virBufferAddLit(&buf, ",cancel-path=");
- virBufferEscape(&buf, ',', ",", "%s", cancel_path);
+ virBufferAddLit(&buf, ",cancel-path=");
+ virBufferEscape(&buf, ',', ",", "%s", cancel_devset);
+ VIR_FREE(cancel_devset);
+ } else {
+ /* all test cases will use this path */
+ virBufferAddLit(&buf, ",path=");
+ virBufferEscape(&buf, ',', ",", "%s", tpmdev);
+
+ virBufferAddLit(&buf, ",cancel-path=");
+ virBufferEscape(&buf, ',', ",", "%s", cancel_path);
+ }
VIR_FREE(cancel_path);
break;
@@ -5970,6 +6066,10 @@ static char *qemuBuildTPMBackendStr(const virDomainDef *def,
emulator, type);
error:
+ VIR_FREE(devset);
+ VIR_FREE(cancel_devset);
+ VIR_FREE(cancel_path);
+
virBufferFreeAndReset(&buf);
return NULL;
}
@@ -9223,13 +9323,35 @@ qemuBuildCommandLine(virConnectPtr conn,
if (def->tpm) {
char *optstr;
+ int tpmfd = -1;
+ int cancelfd = -1;
+ char *fdset;
- if (!(optstr = qemuBuildTPMBackendStr(def, qemuCaps, emulator)))
+ if (!(optstr = qemuBuildTPMBackendStr(def, cmd, qemuCaps, emulator,
+ &tpmfd, &cancelfd)))
goto error;
virCommandAddArgList(cmd, "-tpmdev", optstr, NULL);
VIR_FREE(optstr);
+ if (tpmfd >= 0) {
+ fdset = qemuVirCommandGetFDSet(cmd, tpmfd);
+ if (!fdset)
+ goto error;
+
+ virCommandAddArgList(cmd, "-add-fd", fdset, NULL);
+ VIR_FREE(fdset);
+ }
+
+ if (cancelfd >= 0) {
+ fdset = qemuVirCommandGetFDSet(cmd, cancelfd);
+ if (!fdset)
+ goto error;
+
+ virCommandAddArgList(cmd, "-add-fd", fdset, NULL);
+ VIR_FREE(fdset);
+ }
+
if (!(optstr = qemuBuildTPMDevStr(def, qemuCaps, emulator)))
goto error;
diff --git a/src/util/vircommand.c b/src/util/vircommand.c
index 6527d85..2616446 100644
--- a/src/util/vircommand.c
+++ b/src/util/vircommand.c
@@ -67,6 +67,7 @@ enum {
VIR_EXEC_RUN_SYNC = (1 << 3),
VIR_EXEC_ASYNC_IO = (1 << 4),
VIR_EXEC_LISTEN_FDS = (1 << 5),
+ VIR_EXEC_FIXED_FDS = (1 << 6),
};
typedef struct _virCommandFD virCommandFD;
@@ -214,6 +215,12 @@ virCommandReorderFDs(virCommandPtr cmd)
if (!cmd || cmd->has_error || !cmd->npassfd)
return;
+ if ((cmd->flags & VIR_EXEC_FIXED_FDS)) {
+ virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+ _("The fds are fixed and cannot be reordered"));
+ goto error;
+ }
+
for (i = 0; i < cmd->npassfd; i++)
maxfd = MAX(cmd->passfd[i].fd, maxfd);
@@ -1019,6 +1026,32 @@ virCommandPassListenFDs(virCommandPtr cmd)
cmd->flags |= VIR_EXEC_LISTEN_FDS;
}
+/*
+ * virCommandPassFDGetFDIndex:
+ * @cmd: pointer to virCommand
+ * @fd: FD to get index of
+ *
+ * Determine the index of the FD in the transfer set.
+ *
+ * Returns index >= 0 if @set contains @fd,
+ * -1 otherwise.
+ */
+int
+virCommandPassFDGetFDIndex(virCommandPtr cmd, int fd)
+{
+ size_t i = 0;
+
+ while (i < cmd->npassfd) {
+ if (cmd->passfd[i].fd == fd) {
+ cmd->flags |= VIR_EXEC_FIXED_FDS;
+ return i;
+ }
+ i++;
+ }
+
+ return -1;
+}
+
/**
* virCommandSetPidFile:
* @cmd: the command to modify
diff --git a/src/util/vircommand.h b/src/util/vircommand.h
index bf65de4..198da2f 100644
--- a/src/util/vircommand.h
+++ b/src/util/vircommand.h
@@ -62,6 +62,9 @@ void virCommandPassFD(virCommandPtr cmd,
void virCommandPassListenFDs(virCommandPtr cmd);
+int virCommandPassFDGetFDIndex(virCommandPtr cmd,
+ int fd);
+
void virCommandSetPidFile(virCommandPtr cmd,
const char *pidfile) ATTRIBUTE_NONNULL(2);
--
1.9.3
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