[libvirt] [PATCH 07/10] qemuDomainCreateDevice: Properly deal with symlinks
Michal Privoznik
mprivozn at redhat.com
Fri Jan 20 09:42:47 UTC 2017
Imagine you have a disk with the following source set up:
/dev/disk/by-uuid/$uuid (symlink to) -> /dev/sda
After cbc45525cb21 the transitive end of the symlink chain is
created (/dev/sda), but we need to create any item in chain too.
Others might rely on that.
In this case, /dev/disk/by-uuid/$uuid comes from domain XML thus
it is this path that secdriver tries to relabel. Not the resolved
one.
Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
src/qemu/qemu_domain.c | 150 +++++++++++++++++++++++++++++++++++--------------
1 file changed, 108 insertions(+), 42 deletions(-)
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 0f45f753e..8cbfb2d16 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -68,6 +68,7 @@
#endif
#include <libxml/xpathInternals.h>
+#include "dosname.h"
#define VIR_FROM_THIS VIR_FROM_QEMU
@@ -6958,70 +6959,135 @@ qemuDomainCreateDevice(const char *device,
bool allow_noent)
{
char *devicePath = NULL;
- char *canonDevicePath = NULL;
+ char *target = NULL;
struct stat sb;
int ret = -1;
+ bool isLink = false;
+ bool create = false;
#ifdef WITH_SELINUX
char *tcon = NULL;
#endif
- if (virFileResolveAllLinks(device, &canonDevicePath) < 0) {
+ if (lstat(device, &sb) < 0) {
if (errno == ENOENT && allow_noent) {
/* Ignore non-existent device. */
- ret = 0;
- goto cleanup;
+ return 0;
}
-
- virReportError(errno, _("Unable to canonicalize %s"), device);
- goto cleanup;
- }
-
- if (!STRPREFIX(canonDevicePath, DEVPREFIX)) {
- ret = 0;
- goto cleanup;
+ virReportSystemError(errno, _("Unable to stat %s"), device);
+ return ret;
}
- if (virAsprintf(&devicePath, "%s/%s",
- path, canonDevicePath + strlen(DEVPREFIX)) < 0)
- goto cleanup;
+ isLink = S_ISLNK(sb.st_mode);
- if (stat(canonDevicePath, &sb) < 0) {
- if (errno == ENOENT && allow_noent) {
- /* Ignore non-existent device. */
- ret = 0;
+ /* Here, @device might be whatever path in the system. We
+ * should create the path in the namespace iff its "/dev"
+ * prefixed. However, if it is a symlink, we need to traverse
+ * it too (it might point to something in "/dev"). Just
+ * consider:
+ *
+ * /var/sym1 -> /var/sym2 -> /dev/sda (because users can)
+ *
+ * This means, "/var/sym1" is not created (it's shared with
+ * the parent namespace), nor "/var/sym2", but "/dev/sda".
+ *
+ * TODO Remove all `.' and `..' from the @device path.
+ * Otherwise we might get fooled with `/dev/../var/my_image'.
+ * For now, lets hope callers play nice.
+ */
+ if (STRPREFIX(device, DEVPREFIX)) {
+ if (virAsprintf(&devicePath, "%s/%s",
+ path, device + strlen(DEVPREFIX)) < 0)
goto cleanup;
- }
-
- virReportSystemError(errno, _("Unable to stat %s"), canonDevicePath);
- goto cleanup;
- }
-
- if (virFileMakeParentPath(devicePath) < 0) {
- virReportSystemError(errno,
- _("Unable to create %s"),
- devicePath);
- goto cleanup;
- }
- if (mknod(devicePath, sb.st_mode, sb.st_rdev) < 0) {
- if (errno == EEXIST) {
- ret = 0;
- } else {
+ if (virFileMakeParentPath(devicePath) < 0) {
virReportSystemError(errno,
- _("Failed to make device %s"),
+ _("Unable to create %s"),
devicePath);
+ goto cleanup;
}
+ create = true;
+ }
+
+ if (isLink) {
+ /* We are dealing with a symlink. Create a dangling symlink and descend
+ * down one level which hopefully creates the symlink's target. */
+ if (virFileReadLink(device, &target) < 0) {
+ virReportSystemError(errno,
+ _("unable to resolve symlink %s"),
+ device);
+ goto cleanup;
+ }
+
+ if (create &&
+ symlink(target, devicePath) < 0) {
+ if (errno == EEXIST) {
+ ret = 0;
+ } else {
+ virReportSystemError(errno,
+ _("unable to create symlink %s"),
+ devicePath);
+ }
+ goto cleanup;
+ }
+
+ /* Tricky part. If the target starts with a slash then we need to take
+ * it as it is. Otherwise we need to replace the last component in the
+ * original path with the link target:
+ * /dev/rtc -> rtc0 (want /dev/rtc0)
+ * /dev/disk/by-id/ata-SanDisk_SDSSDXPS480G_161101402485 -> ../../sda
+ * (want /dev/disk/by-id/../../sda)
+ * /dev/stdout -> /proc/self/fd/1 (no change needed)
+ */
+ if (IS_RELATIVE_FILE_NAME(target)) {
+ char *c = NULL, *tmp = NULL, *devTmp = NULL;
+
+ if (VIR_STRDUP(devTmp, device) < 0)
+ goto cleanup;
+
+ if ((c = strrchr(devTmp, '/')))
+ *(c + 1) = '\0';
+
+ if (virAsprintf(&tmp, "%s%s", devTmp, target) < 0) {
+ VIR_FREE(devTmp);
+ goto cleanup;
+ }
+ VIR_FREE(devTmp);
+ VIR_FREE(target);
+ target = tmp;
+ tmp = NULL;
+ }
+
+ if (qemuDomainCreateDevice(target, path, allow_noent) < 0)
+ goto cleanup;
+ } else {
+ if (create &&
+ mknod(devicePath, sb.st_mode, sb.st_rdev) < 0) {
+ if (errno == EEXIST) {
+ ret = 0;
+ } else {
+ virReportSystemError(errno,
+ _("Failed to make device %s"),
+ devicePath);
+ }
+ goto cleanup;
+ }
+ }
+
+ if (!create) {
+ ret = 0;
goto cleanup;
}
- if (chown(devicePath, sb.st_uid, sb.st_gid) < 0) {
+ if (lchown(devicePath, sb.st_uid, sb.st_gid) < 0) {
virReportSystemError(errno,
_("Failed to chown device %s"),
devicePath);
goto cleanup;
}
- if (virFileCopyACLs(canonDevicePath, devicePath) < 0 &&
+ /* Symlinks don't have ACLs. */
+ if (!isLink &&
+ virFileCopyACLs(device, devicePath) < 0 &&
errno != ENOTSUP) {
virReportSystemError(errno,
_("Failed to copy ACLs on device %s"),
@@ -7030,16 +7096,16 @@ qemuDomainCreateDevice(const char *device,
}
#ifdef WITH_SELINUX
- if (getfilecon_raw(canonDevicePath, &tcon) < 0 &&
+ if (lgetfilecon_raw(device, &tcon) < 0 &&
(errno != ENOTSUP && errno != ENODATA)) {
virReportSystemError(errno,
_("Unable to get SELinux label from %s"),
- canonDevicePath);
+ device);
goto cleanup;
}
if (tcon &&
- setfilecon_raw(devicePath, (VIR_SELINUX_CTX_CONST char *) tcon) < 0) {
+ lsetfilecon_raw(devicePath, (VIR_SELINUX_CTX_CONST char *) tcon) < 0) {
VIR_WARNINGS_NO_WLOGICALOP_EQUAL_EXPR
if (errno != EOPNOTSUPP && errno != ENOTSUP) {
VIR_WARNINGS_RESET
@@ -7053,7 +7119,7 @@ qemuDomainCreateDevice(const char *device,
ret = 0;
cleanup:
- VIR_FREE(canonDevicePath);
+ VIR_FREE(target);
VIR_FREE(devicePath);
#ifdef WITH_SELINUX
freecon(tcon);
--
2.11.0
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