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qemuDomainCreateDevice: Properly deal with symlinks

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Imagine you have a disk with the following source set up:

/dev/disk/by-uuid/$uuid (symlink to) -> /dev/sda

After cbc45525cb 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@redhat.com>
This commit is contained in:
Michal Privoznik 2017-01-18 19:58:02 +01:00
parent b621291f5c
commit 54ed672214
1 changed files with 111 additions and 45 deletions
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156
src/qemu/qemu_domain.c
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@ -69,6 +69,7 @@
#endif
#include <libxml/xpathInternals.h>
#include "dosname.h"
#define VIR_FROM_THIS VIR_FROM_QEMU
@ -7003,70 +7004,135 @@ 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;
return 0;
}
virReportSystemError(errno, _("Unable to stat %s"), device);
return ret;
}
isLink = S_ISLNK(sb.st_mode);
/* Here, @device might be whatever path in the system. We
* should create the path in the namespace iff it's "/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;
if (virFileMakeParentPath(devicePath) < 0) {
virReportSystemError(errno,
_("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;
}
virReportError(errno, _("Unable to canonicalize %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 (!STRPREFIX(canonDevicePath, DEVPREFIX)) {
if (!create) {
ret = 0;
goto cleanup;
}
if (virAsprintf(&devicePath, "%s/%s",
path, canonDevicePath + strlen(DEVPREFIX)) < 0)
goto cleanup;
if (stat(canonDevicePath, &sb) < 0) {
if (errno == ENOENT && allow_noent) {
/* Ignore non-existent device. */
ret = 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 {
virReportSystemError(errno,
_("Failed to make device %s"),
devicePath);
}
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"),
@ -7075,16 +7141,16 @@ 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
@ -7098,7 +7164,7 @@ qemuDomainCreateDevice(const char *device,
ret = 0;
cleanup:
VIR_FREE(canonDevicePath);
VIR_FREE(target);
VIR_FREE(devicePath);
#ifdef WITH_SELINUX
freecon(tcon);