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qemuDomainAttachDeviceMknodRecursive: Isolate bind mounted devices condition

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When attaching a device into a domain, the corresponding /dev
node might need to be created in the domain's namespace. For some
types of files we call mknod(), for symlinks we call symlink(),
but for others - which exist in the host namespace - we need to
so called 'bind mount' them (which is a way of passing a
file/directory between mount namespaces). There is this condition
in qemuDomainAttachDeviceMknodRecursive() which decides whether a
bind mount will be used, move it into a separate function so that
it can be reused later.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
This commit is contained in:
Michal Privoznik 2020-07-21 09:44:36 +02:00
parent 08277c2bc6
commit bf9aeab4f0
1 changed files with 15 additions and 6 deletions
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21
src/qemu/qemu_namespace.c
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@ -1253,6 +1253,17 @@ qemuDomainAttachDeviceMknodHelper(pid_t pid G_GNUC_UNUSED,
} }
static bool
qemuNamespaceMknodItemNeedsBindMount(mode_t st_mode)
{
/* A block device S_ISBLK() or a chardev S_ISCHR() is intentionally not
* handled. We want to mknod() it instead of passing in through bind
* mounting. */
return S_ISREG(st_mode) || S_ISFIFO(st_mode) ||
S_ISSOCK(st_mode) || S_ISDIR(st_mode);
}
static int static int
qemuDomainAttachDeviceMknodRecursive(virQEMUDriverPtr driver, qemuDomainAttachDeviceMknodRecursive(virQEMUDriverPtr driver,
virDomainObjPtr vm, virDomainObjPtr vm,
@ -1266,8 +1277,7 @@ qemuDomainAttachDeviceMknodRecursive(virQEMUDriverPtr driver,
int ret = -1; int ret = -1;
g_autofree char *target = NULL; g_autofree char *target = NULL;
bool isLink; bool isLink;
bool isReg; bool needsBindMount;
bool isDir;
if (!ttl) { if (!ttl) {
virReportSystemError(ELOOP, virReportSystemError(ELOOP,
@ -1289,10 +1299,9 @@ qemuDomainAttachDeviceMknodRecursive(virQEMUDriverPtr driver,
} }
isLink = S_ISLNK(data.sb.st_mode); isLink = S_ISLNK(data.sb.st_mode);
isReg = S_ISREG(data.sb.st_mode) || S_ISFIFO(data.sb.st_mode) || S_ISSOCK(data.sb.st_mode); needsBindMount = qemuNamespaceMknodItemNeedsBindMount(data.sb.st_mode);
isDir = S_ISDIR(data.sb.st_mode);
if ((isReg || isDir) && STRPREFIX(file, QEMU_DEVPREFIX)) { if (needsBindMount && STRPREFIX(file, QEMU_DEVPREFIX)) {
cfg = virQEMUDriverGetConfig(driver); cfg = virQEMUDriverGetConfig(driver);
if (!(target = qemuDomainGetPreservedMountPath(cfg, vm, file))) if (!(target = qemuDomainGetPreservedMountPath(cfg, vm, file)))
goto cleanup; goto cleanup;
@ -1382,7 +1391,7 @@ qemuDomainAttachDeviceMknodRecursive(virQEMUDriverPtr driver,
freecon(data.tcon); freecon(data.tcon);
# endif # endif
virFileFreeACLs(&data.acl); virFileFreeACLs(&data.acl);
if (isReg && target) if (needsBindMount && target)
umount(target); umount(target);
return ret; return ret;
} }