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libvirt/src/util/virstoragefile.c
Eric Blake d1333dd0fb storage: don't follow backing chain symlinks too eagerly 
If you have a qcow2 file /path1/to/file pointed to by symlink
/path2/symlink, and pass qemu /path2/symlink, then qemu treats
a relative backing file in the qcow2 metadata as being relative
to /path2, not /path1/to.  Yes, this means that it is possible
to create a qcow2 file where the choice of WHICH directory and
symlink you access its contents from will then determine WHICH
backing file (if any) you actually find; the results can be
rather screwy, but we have to match what qemu does.

Libvirt and qemu default to creating absolute backing file
names, so most users don't hit this.  But at least VDSM uses
symlinks and relative backing names alongside the
--reuse-external flags to libvirt snapshot operations, with the
result that libvirt was failing to follow the intended chain of
backing files, and then backing files were not granted the
necessary sVirt permissions to be opened by qemu.

See https://bugzilla.redhat.com/show_bug.cgi?id=903248 for
more gory details.  This fixes a regression introduced in
commit 8250783.

I tested this patch by creating the following chain:

ls /home/eblake/Downloads/Fedora.iso # raw file for base
cd /var/lib/libvirt/images
qemu-img create -f qcow2 \
  -obacking_file=/home/eblake/Downloads/Fedora.iso,backing_fmt=raw one
mkdir sub
cd sub
ln -s ../one onelink
qemu-img create -f qcow2 \
  -obacking_file=../sub/onelink,backing_fmt=qcow2 two
mv two ..
ln -s ../two twolink
qemu-img create -f qcow2 \
  -obacking_file=../sub/twolink,backing_fmt=qcow2 three
mv three ..
ln -s ../three threelink

then pointing my domain at /var/lib/libvirt/images/sub/threelink.
Prior to this patch, I got complaints about missing backing
files; afterwards, I was able to verify that the backing chain
(and hence DAC and SELinux relabels) of the entire chain worked.

* src/util/virstoragefile.h (_virStorageFileMetadata): Add
directory member.
* src/util/virstoragefile.c (absolutePathFromBaseFile): Drop,
replaced by...
(virFindBackingFile): ...better function.
(virStorageFileGetMetadataInternal): Add an argument.
(virStorageFileGetMetadataFromFD, virStorageFileChainLookup)
(virStorageFileGetMetadata): Update callers.
2013-02-15 16:07:01 -07:00

1365 lines
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/*
* virstoragefile.c: file utility functions for FS storage backend
*
* Copyright (C) 2007-2013 Red Hat, Inc.
* Copyright (C) 2007-2008 Daniel P. Berrange
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see
* <http://www.gnu.org/licenses/>.
*
* Author: Daniel P. Berrange <berrange@redhat.com>
*/
#include <config.h>
#include "virstoragefile.h"
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#ifdef __linux__
# if HAVE_LINUX_MAGIC_H
# include <linux/magic.h>
# endif
# include <sys/statfs.h>
#endif
#include "dirname.h"
#include "viralloc.h"
#include "virerror.h"
#include "virlog.h"
#include "virfile.h"
#include "c-ctype.h"
#include "vircommand.h"
#include "virhash.h"
#include "virendian.h"
#define VIR_FROM_THIS VIR_FROM_STORAGE
VIR_ENUM_IMPL(virStorageFileFormat,
VIR_STORAGE_FILE_LAST,
"none",
"raw", "dir", "bochs",
"cloop", "cow", "dmg", "iso",
"qcow", "qcow2", "qed", "vmdk", "vpc",
"fat", "vhd", "vdi")
enum lv_endian {
LV_LITTLE_ENDIAN = 1, /* 1234 */
LV_BIG_ENDIAN /* 4321 */
};
enum {
BACKING_STORE_OK,
BACKING_STORE_INVALID,
BACKING_STORE_ERROR,
};
/* Either 'magic' or 'extension' *must* be provided */
struct FileTypeInfo {
int magicOffset; /* Byte offset of the magic */
const char *magic; /* Optional string of file magic
* to check at head of file */
const char *extension; /* Optional file extension to check */
enum lv_endian endian; /* Endianness of file format */
int versionOffset; /* Byte offset from start of file
* where we find version number,
* -1 to skip version test */
int versionNumber; /* Version number to validate */
int sizeOffset; /* Byte offset from start of file
* where we find capacity info,
* -1 to use st_size as capacity */
int sizeBytes; /* Number of bytes for size field */
int sizeMultiplier; /* A scaling factor if size is not in bytes */
/* Store a COW base image path (possibly relative),
* or NULL if there is no COW base image, to RES;
* return BACKING_STORE_* */
int qcowCryptOffset; /* Byte offset from start of file
* where to find encryption mode,
* -1 if encryption is not used */
int (*getBackingStore)(char **res, int *format,
const unsigned char *buf, size_t buf_size);
};
static int cowGetBackingStore(char **, int *,
const unsigned char *, size_t);
static int qcow1GetBackingStore(char **, int *,
const unsigned char *, size_t);
static int qcow2GetBackingStore(char **, int *,
const unsigned char *, size_t);
static int vmdk4GetBackingStore(char **, int *,
const unsigned char *, size_t);
static int
qedGetBackingStore(char **, int *, const unsigned char *, size_t);
#define QCOWX_HDR_VERSION (4)
#define QCOWX_HDR_BACKING_FILE_OFFSET (QCOWX_HDR_VERSION+4)
#define QCOWX_HDR_BACKING_FILE_SIZE (QCOWX_HDR_BACKING_FILE_OFFSET+8)
#define QCOWX_HDR_IMAGE_SIZE (QCOWX_HDR_BACKING_FILE_SIZE+4+4)
#define QCOW1_HDR_CRYPT (QCOWX_HDR_IMAGE_SIZE+8+1+1)
#define QCOW2_HDR_CRYPT (QCOWX_HDR_IMAGE_SIZE+8)
#define QCOW1_HDR_TOTAL_SIZE (QCOW1_HDR_CRYPT+4+8)
#define QCOW2_HDR_TOTAL_SIZE (QCOW2_HDR_CRYPT+4+4+8+8+4+4+8)
#define QCOW2_HDR_EXTENSION_END 0
#define QCOW2_HDR_EXTENSION_BACKING_FORMAT 0xE2792ACA
#define QED_HDR_FEATURES_OFFSET (4+4+4+4)
#define QED_HDR_IMAGE_SIZE (QED_HDR_FEATURES_OFFSET+8+8+8+8)
#define QED_HDR_BACKING_FILE_OFFSET (QED_HDR_IMAGE_SIZE+8)
#define QED_HDR_BACKING_FILE_SIZE (QED_HDR_BACKING_FILE_OFFSET+4)
#define QED_F_BACKING_FILE 0x01
#define QED_F_BACKING_FORMAT_NO_PROBE 0x04
/* VMDK needs at least 20*512 B to find backing store,
* ISO has 5 Byte magic on offset 32769,
* other formats need less */
#define STORAGE_MAX_HEAD 32769+5
static struct FileTypeInfo const fileTypeInfo[] = {
[VIR_STORAGE_FILE_NONE] = { 0, NULL, NULL, LV_LITTLE_ENDIAN,
-1, 0, 0, 0, 0, 0, NULL },
[VIR_STORAGE_FILE_RAW] = { 0, NULL, NULL, LV_LITTLE_ENDIAN,
-1, 0, 0, 0, 0, 0, NULL },
[VIR_STORAGE_FILE_DIR] = { 0, NULL, NULL, LV_LITTLE_ENDIAN,
-1, 0, 0, 0, 0, 0, NULL },
[VIR_STORAGE_FILE_BOCHS] = {
/*"Bochs Virtual HD Image", */ /* Untested */
0, NULL, NULL,
LV_LITTLE_ENDIAN, 64, 0x20000,
32+16+16+4+4+4+4+4, 8, 1, -1, NULL
},
[VIR_STORAGE_FILE_CLOOP] = {
/* #!/bin/sh
#V2.0 Format
modprobe cloop file=$0 && mount -r -t iso9660 /dev/cloop $1
*/ /* Untested */
0, NULL, NULL,
LV_LITTLE_ENDIAN, -1, 0,
-1, 0, 0, -1, NULL
},
[VIR_STORAGE_FILE_COW] = {
0, "OOOM", NULL,
LV_BIG_ENDIAN, 4, 2,
4+4+1024+4, 8, 1, -1, cowGetBackingStore
},
[VIR_STORAGE_FILE_DMG] = {
/* XXX QEMU says there's no magic for dmg,
* /usr/share/misc/magic lists double magic (both offsets
* would have to match) but then disables that check. */
0, NULL, ".dmg",
0, -1, 0,
-1, 0, 0, -1, NULL
},
[VIR_STORAGE_FILE_ISO] = {
32769, "CD001", ".iso",
LV_LITTLE_ENDIAN, -2, 0,
-1, 0, 0, -1, NULL
},
[VIR_STORAGE_FILE_QCOW] = {
0, "QFI", NULL,
LV_BIG_ENDIAN, 4, 1,
QCOWX_HDR_IMAGE_SIZE, 8, 1, QCOW1_HDR_CRYPT, qcow1GetBackingStore,
},
[VIR_STORAGE_FILE_QCOW2] = {
0, "QFI", NULL,
LV_BIG_ENDIAN, 4, 2,
QCOWX_HDR_IMAGE_SIZE, 8, 1, QCOW2_HDR_CRYPT, qcow2GetBackingStore,
},
[VIR_STORAGE_FILE_QED] = {
/* http://wiki.qemu.org/Features/QED */
0, "QED", NULL,
LV_LITTLE_ENDIAN, -2, -1,
QED_HDR_IMAGE_SIZE, 8, 1, -1, qedGetBackingStore,
},
[VIR_STORAGE_FILE_VMDK] = {
0, "KDMV", NULL,
LV_LITTLE_ENDIAN, 4, 1,
4+4+4, 8, 512, -1, vmdk4GetBackingStore
},
[VIR_STORAGE_FILE_VPC] = {
0, "conectix", NULL,
LV_BIG_ENDIAN, 12, 0x10000,
8 + 4 + 4 + 8 + 4 + 4 + 2 + 2 + 4, 8, 1, -1, NULL
},
/* TODO: add getBackingStore function */
[VIR_STORAGE_FILE_VDI] = {
64, "\x7f\x10\xda\xbe", ".vdi",
LV_LITTLE_ENDIAN, 68, 0x00010001,
68 + 5 * 4 + 256 + 7 * 4, 8, 1, -1, NULL},
/* Not direct file formats, but used for various drivers */
[VIR_STORAGE_FILE_FAT] = { 0, NULL, NULL, LV_LITTLE_ENDIAN,
-1, 0, 0, 0, 0, 0, NULL },
[VIR_STORAGE_FILE_VHD] = { 0, NULL, NULL, LV_LITTLE_ENDIAN,
-1, 0, 0, 0, 0, 0, NULL },
};
verify(ARRAY_CARDINALITY(fileTypeInfo) == VIR_STORAGE_FILE_LAST);
static int
cowGetBackingStore(char **res,
int *format,
const unsigned char *buf,
size_t buf_size)
{
#define COW_FILENAME_MAXLEN 1024
*res = NULL;
*format = VIR_STORAGE_FILE_AUTO;
if (buf_size < 4+4+ COW_FILENAME_MAXLEN)
return BACKING_STORE_INVALID;
if (buf[4+4] == '\0') { /* cow_header_v2.backing_file[0] */
*format = VIR_STORAGE_FILE_NONE;
return BACKING_STORE_OK;
}
*res = strndup((const char*)buf + 4+4, COW_FILENAME_MAXLEN);
if (*res == NULL) {
virReportOOMError();
return BACKING_STORE_ERROR;
}
return BACKING_STORE_OK;
}
static int
qcow2GetBackingStoreFormat(int *format,
const unsigned char *buf,
size_t buf_size,
size_t extension_start,
size_t extension_end)
{
size_t offset = extension_start;
/*
* The extensions take format of
*
* int32: magic
* int32: length
* byte[length]: payload
*
* Unknown extensions can be ignored by skipping
* over "length" bytes in the data stream.
*/
while (offset < (buf_size-8) &&
offset < (extension_end-8)) {
unsigned int magic = virReadBufInt32BE(buf + offset);
unsigned int len = virReadBufInt32BE(buf + offset + 4);
offset += 8;
if ((offset + len) < offset)
break;
if ((offset + len) > buf_size)
break;
switch (magic) {
case QCOW2_HDR_EXTENSION_END:
goto done;
case QCOW2_HDR_EXTENSION_BACKING_FORMAT:
if (buf[offset+len] != '\0')
break;
*format = virStorageFileFormatTypeFromString(
((const char *)buf)+offset);
if (*format <= VIR_STORAGE_FILE_NONE)
return -1;
}
offset += len;
}
done:
return 0;
}
static int
qcowXGetBackingStore(char **res,
int *format,
const unsigned char *buf,
size_t buf_size,
bool isQCow2)
{
unsigned long long offset;
unsigned int size;
*res = NULL;
if (format)
*format = VIR_STORAGE_FILE_AUTO;
if (buf_size < QCOWX_HDR_BACKING_FILE_OFFSET+8+4)
return BACKING_STORE_INVALID;
offset = virReadBufInt64BE(buf + QCOWX_HDR_BACKING_FILE_OFFSET);
if (offset > buf_size)
return BACKING_STORE_INVALID;
size = virReadBufInt32BE(buf + QCOWX_HDR_BACKING_FILE_SIZE);
if (size == 0) {
if (format)
*format = VIR_STORAGE_FILE_NONE;
return BACKING_STORE_OK;
}
if (offset + size > buf_size || offset + size < offset)
return BACKING_STORE_INVALID;
if (size + 1 == 0)
return BACKING_STORE_INVALID;
if (VIR_ALLOC_N(*res, size + 1) < 0) {
virReportOOMError();
return BACKING_STORE_ERROR;
}
memcpy(*res, buf + offset, size);
(*res)[size] = '\0';
/*
* Traditionally QCow2 files had a layout of
*
* [header]
* [backingStoreName]
*
* Although the backingStoreName typically followed
* the header immediately, this was not required by
* the format. By specifying a higher byte offset for
* the backing file offset in the header, it was
* possible to leave space between the header and
* start of backingStore.
*
* This hack is now used to store extensions to the
* qcow2 format:
*
* [header]
* [extensions]
* [backingStoreName]
*
* Thus the file region to search for extensions is
* between the end of the header (QCOW2_HDR_TOTAL_SIZE)
* and the start of the backingStoreName (offset)
*/
if (isQCow2 && format &&
qcow2GetBackingStoreFormat(format, buf, buf_size, QCOW2_HDR_TOTAL_SIZE,
offset) < 0)
return BACKING_STORE_INVALID;
return BACKING_STORE_OK;
}
static int
qcow1GetBackingStore(char **res,
int *format,
const unsigned char *buf,
size_t buf_size)
{
int ret;
/* QCow1 doesn't have the extensions capability
* used to store backing format */
*format = VIR_STORAGE_FILE_AUTO;
ret = qcowXGetBackingStore(res, NULL, buf, buf_size, false);
if (ret == 0 && *buf == '\0')
*format = VIR_STORAGE_FILE_NONE;
return ret;
}
static int
qcow2GetBackingStore(char **res,
int *format,
const unsigned char *buf,
size_t buf_size)
{
return qcowXGetBackingStore(res, format, buf, buf_size, true);
}
static int
vmdk4GetBackingStore(char **res,
int *format,
const unsigned char *buf,
size_t buf_size)
{
static const char prefix[] = "parentFileNameHint=\"";
char *desc, *start, *end;
size_t len;
int ret = BACKING_STORE_ERROR;
if (VIR_ALLOC_N(desc, STORAGE_MAX_HEAD + 1) < 0) {
virReportOOMError();
goto cleanup;
}
*res = NULL;
/*
* Technically this should have been VMDK, since
* VMDK spec / VMWare impl only support VMDK backed
* by VMDK. QEMU isn't following this though and
* does probing on VMDK backing files, hence we set
* AUTO
*/
*format = VIR_STORAGE_FILE_AUTO;
if (buf_size <= 0x200) {
ret = BACKING_STORE_INVALID;
goto cleanup;
}
len = buf_size - 0x200;
if (len > STORAGE_MAX_HEAD)
len = STORAGE_MAX_HEAD;
memcpy(desc, buf + 0x200, len);
desc[len] = '\0';
start = strstr(desc, prefix);
if (start == NULL) {
*format = VIR_STORAGE_FILE_NONE;
ret = BACKING_STORE_OK;
goto cleanup;
}
start += strlen(prefix);
end = strchr(start, '"');
if (end == NULL) {
ret = BACKING_STORE_INVALID;
goto cleanup;
}
if (end == start) {
*format = VIR_STORAGE_FILE_NONE;
ret = BACKING_STORE_OK;
goto cleanup;
}
*end = '\0';
*res = strdup(start);
if (*res == NULL) {
virReportOOMError();
goto cleanup;
}
ret = BACKING_STORE_OK;
cleanup:
VIR_FREE(desc);
return ret;
}
static int
qedGetBackingStore(char **res,
int *format,
const unsigned char *buf,
size_t buf_size)
{
unsigned long long flags;
unsigned long offset, size;
*res = NULL;
/* Check if this image has a backing file */
if (buf_size < QED_HDR_FEATURES_OFFSET+8)
return BACKING_STORE_INVALID;
flags = virReadBufInt64LE(buf + QED_HDR_FEATURES_OFFSET);
if (!(flags & QED_F_BACKING_FILE)) {
*format = VIR_STORAGE_FILE_NONE;
return BACKING_STORE_OK;
}
/* Parse the backing file */
if (buf_size < QED_HDR_BACKING_FILE_OFFSET+8)
return BACKING_STORE_INVALID;
offset = virReadBufInt32LE(buf + QED_HDR_BACKING_FILE_OFFSET);
if (offset > buf_size)
return BACKING_STORE_INVALID;
size = virReadBufInt32LE(buf + QED_HDR_BACKING_FILE_SIZE);
if (size == 0)
return BACKING_STORE_OK;
if (offset + size > buf_size || offset + size < offset)
return BACKING_STORE_INVALID;
if (VIR_ALLOC_N(*res, size + 1) < 0) {
virReportOOMError();
return BACKING_STORE_ERROR;
}
memcpy(*res, buf + offset, size);
(*res)[size] = '\0';
if (flags & QED_F_BACKING_FORMAT_NO_PROBE)
*format = VIR_STORAGE_FILE_RAW;
else
*format = VIR_STORAGE_FILE_AUTO_SAFE;
return BACKING_STORE_OK;
}
/**
* Given a starting point START (either an original file name, or the
* directory containing the original name, depending on START_IS_DIR)
* and a possibly relative backing file NAME, compute the relative
* DIRECTORY (optional) and CANONICAL (mandatory) location of the
* backing file. Return 0 on success, negative on error.
*/
static int ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(3) ATTRIBUTE_NONNULL(5)
virFindBackingFile(const char *start, bool start_is_dir, const char *path,
char **directory, char **canonical)
{
char *combined = NULL;
int ret = -1;
if (*path == '/') {
/* Safe to cast away const */
combined = (char *)path;
} else {
size_t d_len = start_is_dir ? strlen(start) : dir_len(start);
if (d_len > INT_MAX) {
virReportError(VIR_ERR_INTERNAL_ERROR,
_("name too long: '%s'"), start);
goto cleanup;
} else if (d_len == 0) {
start = ".";
d_len = 1;
}
if (virAsprintf(&combined, "%.*s/%s", (int)d_len, start, path) < 0) {
virReportOOMError();
goto cleanup;
}
}
if (directory && !(*directory = mdir_name(combined))) {
virReportOOMError();
goto cleanup;
}
if (!(*canonical = canonicalize_file_name(combined))) {
virReportSystemError(errno,
_("Can't canonicalize path '%s'"), path);
goto cleanup;
}
ret = 0;
cleanup:
if (combined != path)
VIR_FREE(combined);
return ret;
}
static bool
virStorageFileMatchesMagic(int format,
unsigned char *buf,
size_t buflen)
{
int mlen;
int magicOffset = fileTypeInfo[format].magicOffset;
const char *magic = fileTypeInfo[format].magic;
if (magic == NULL)
return false;
/* Validate magic data */
mlen = strlen(magic);
if (magicOffset + mlen > buflen)
return false;
if (memcmp(buf + magicOffset, magic, mlen) != 0)
return false;
return true;
}
static bool
virStorageFileMatchesExtension(int format,
const char *path)
{
if (fileTypeInfo[format].extension == NULL)
return false;
if (virFileHasSuffix(path, fileTypeInfo[format].extension))
return true;
return false;
}
static bool
virStorageFileMatchesVersion(int format,
unsigned char *buf,
size_t buflen)
{
int version;
/* Validate version number info */
if (fileTypeInfo[format].versionOffset == -1)
return false;
/* -2 == non-versioned file format, so trivially match */
if (fileTypeInfo[format].versionOffset == -2)
return true;
if ((fileTypeInfo[format].versionOffset + 4) > buflen)
return false;
if (fileTypeInfo[format].endian == LV_LITTLE_ENDIAN)
version = virReadBufInt32LE(buf + fileTypeInfo[format].versionOffset);
else
version = virReadBufInt32BE(buf + fileTypeInfo[format].versionOffset);
VIR_DEBUG("Compare detected version %d vs expected version %d",
version, fileTypeInfo[format].versionNumber);
if (version != fileTypeInfo[format].versionNumber)
return false;
return true;
}
static bool
virBackingStoreIsFile(const char *backing)
{
/* Backing store is a network block device or Rados block device */
if (STRPREFIX(backing, "nbd:") || STRPREFIX(backing, "rbd:"))
return false;
return true;
}
static int
virStorageFileProbeFormatFromBuf(const char *path,
unsigned char *buf,
size_t buflen)
{
int format = VIR_STORAGE_FILE_RAW;
int i;
int possibleFormat = VIR_STORAGE_FILE_RAW;
VIR_DEBUG("path=%s", path);
/* First check file magic */
for (i = 0 ; i < VIR_STORAGE_FILE_LAST ; i++) {
if (virStorageFileMatchesMagic(i, buf, buflen)) {
if (!virStorageFileMatchesVersion(i, buf, buflen)) {
possibleFormat = i;
continue;
}
format = i;
goto cleanup;
}
}
if (possibleFormat != VIR_STORAGE_FILE_RAW)
VIR_WARN("File %s matches %s magic, but version is wrong. "
"Please report new version to libvir-list@redhat.com",
path, virStorageFileFormatTypeToString(possibleFormat));
/* No magic, so check file extension */
for (i = 0 ; i < VIR_STORAGE_FILE_LAST ; i++) {
if (virStorageFileMatchesExtension(i, path)) {
format = i;
goto cleanup;
}
}
cleanup:
VIR_DEBUG("format=%d", format);
return format;
}
/* Given a file descriptor FD open on PATH, and optionally opened from
* a given DIRECTORY, return metadata about that file, assuming it has
* the given FORMAT. */
static virStorageFileMetadataPtr
virStorageFileGetMetadataInternal(const char *path,
int fd,
const char *directory,
int format)
{
virStorageFileMetadata *meta = NULL;
unsigned char *buf = NULL;
ssize_t len = STORAGE_MAX_HEAD;
virStorageFileMetadata *ret = NULL;
struct stat sb;
VIR_DEBUG("path=%s, fd=%d, format=%d", path, fd, format);
if (VIR_ALLOC(meta) < 0) {
virReportOOMError();
return NULL;
}
if (fstat(fd, &sb) < 0) {
virReportSystemError(errno,
_("cannot stat file '%s'"),
path);
goto cleanup;
}
/* No header to probe for directories, but also no backing file */
if (S_ISDIR(sb.st_mode))
return meta;
if (lseek(fd, 0, SEEK_SET) == (off_t)-1) {
virReportSystemError(errno, _("cannot seek to start of '%s'"), path);
goto cleanup;
}
if (VIR_ALLOC_N(buf, len) < 0) {
virReportOOMError();
goto cleanup;
}
if ((len = read(fd, buf, len)) < 0) {
virReportSystemError(errno, _("cannot read header '%s'"), path);
goto cleanup;
}
if (format == VIR_STORAGE_FILE_AUTO)
format = virStorageFileProbeFormatFromBuf(path, buf, len);
if (format <= VIR_STORAGE_FILE_NONE ||
format >= VIR_STORAGE_FILE_LAST) {
virReportSystemError(EINVAL, _("unknown storage file format %d"),
format);
goto cleanup;
}
/* XXX we should consider moving virStorageBackendUpdateVolInfo
* code into this method, for non-magic files
*/
if (!fileTypeInfo[format].magic)
goto done;
/* Optionally extract capacity from file */
if (fileTypeInfo[format].sizeOffset != -1) {
if ((fileTypeInfo[format].sizeOffset + 8) > len)
goto done;
if (fileTypeInfo[format].endian == LV_LITTLE_ENDIAN)
meta->capacity = virReadBufInt64LE(buf +
fileTypeInfo[format].sizeOffset);
else
meta->capacity = virReadBufInt64BE(buf +
fileTypeInfo[format].sizeOffset);
/* Avoid unlikely, but theoretically possible overflow */
if (meta->capacity > (ULLONG_MAX /
fileTypeInfo[format].sizeMultiplier))
goto done;
meta->capacity *= fileTypeInfo[format].sizeMultiplier;
}
if (fileTypeInfo[format].qcowCryptOffset != -1) {
int crypt_format;
crypt_format = virReadBufInt32BE(buf +
fileTypeInfo[format].qcowCryptOffset);
meta->encrypted = crypt_format != 0;
}
if (fileTypeInfo[format].getBackingStore != NULL) {
char *backing;
int backingFormat;
int store = fileTypeInfo[format].getBackingStore(&backing,
&backingFormat,
buf, len);
if (store == BACKING_STORE_INVALID)
goto done;
if (store == BACKING_STORE_ERROR)
goto cleanup;
meta->backingStoreIsFile = false;
if (backing != NULL) {
meta->backingStore = strdup(backing);
if (meta->backingStore == NULL) {
virReportOOMError();
VIR_FREE(backing);
goto cleanup;
}
if (virBackingStoreIsFile(backing)) {
meta->backingStoreIsFile = true;
meta->backingStoreRaw = meta->backingStore;
meta->backingStore = NULL;
if (virFindBackingFile(directory ? directory : path,
!!directory, backing,
&meta->directory,
&meta->backingStore) < 0) {
/* the backing file is (currently) unavailable, treat this
* file as standalone:
* backingStoreRaw is kept to mark broken image chains */
meta->backingStoreIsFile = false;
backingFormat = VIR_STORAGE_FILE_NONE;
VIR_WARN("Backing file '%s' of image '%s' is missing.",
meta->backingStoreRaw, path);
}
}
VIR_FREE(backing);
meta->backingStoreFormat = backingFormat;
} else {
meta->backingStore = NULL;
meta->backingStoreFormat = VIR_STORAGE_FILE_NONE;
}
}
done:
ret = meta;
meta = NULL;
cleanup:
virStorageFileFreeMetadata(meta);
VIR_FREE(buf);
return ret;
}
/**
* virStorageFileProbeFormatFromFD:
*
* Probe for the format of 'fd' (which is an open file descriptor
* pointing to 'path'), returning the detected disk format.
*
* Callers are advised never to trust the returned 'format'
* unless it is listed as VIR_STORAGE_FILE_RAW, since a
* malicious guest can turn a file into any other non-raw
* format at will.
*
* Best option: Don't use this function
*/
int
virStorageFileProbeFormatFromFD(const char *path, int fd)
{
unsigned char *head;
ssize_t len = STORAGE_MAX_HEAD;
int ret = -1;
struct stat sb;
if (fstat(fd, &sb) < 0) {
virReportSystemError(errno,
_("cannot stat file '%s'"),
path);
return -1;
}
/* No header to probe for directories */
if (S_ISDIR(sb.st_mode)) {
return VIR_STORAGE_FILE_DIR;
}
if (VIR_ALLOC_N(head, len) < 0) {
virReportOOMError();
return -1;
}
if (lseek(fd, 0, SEEK_SET) == (off_t)-1) {
virReportSystemError(errno, _("cannot set to start of '%s'"), path);
goto cleanup;
}
if ((len = read(fd, head, len)) < 0) {
virReportSystemError(errno, _("cannot read header '%s'"), path);
goto cleanup;
}
ret = virStorageFileProbeFormatFromBuf(path, head, len);
cleanup:
VIR_FREE(head);
return ret;
}
/**
* virStorageFileProbeFormat:
*
* Probe for the format of 'path', returning the detected
* disk format.
*
* Callers are advised never to trust the returned 'format'
* unless it is listed as VIR_STORAGE_FILE_RAW, since a
* malicious guest can turn a raw file into any other non-raw
* format at will.
*
* Best option: Don't use this function
*/
int
virStorageFileProbeFormat(const char *path, uid_t uid, gid_t gid)
{
int fd, ret;
if ((fd = virFileOpenAs(path, O_RDONLY, 0, uid, gid, 0)) < 0) {
virReportSystemError(errno, _("cannot open file '%s'"), path);
return -1;
}
ret = virStorageFileProbeFormatFromFD(path, fd);
VIR_FORCE_CLOSE(fd);
return ret;
}
/**
* virStorageFileGetMetadataFromFD:
*
* Extract metadata about the storage volume with the specified
* image format. If image format is VIR_STORAGE_FILE_AUTO, it
* will probe to automatically identify the format. Does not recurse.
*
* Callers are advised never to use VIR_STORAGE_FILE_AUTO as a
* format, since a malicious guest can turn a raw file into any
* other non-raw format at will.
*
* If the returned meta.backingStoreFormat is VIR_STORAGE_FILE_AUTO
* it indicates the image didn't specify an explicit format for its
* backing store. Callers are advised against probing for the
* backing store format in this case.
*
* Caller MUST free the result after use via virStorageFileFreeMetadata.
*/
virStorageFileMetadataPtr
virStorageFileGetMetadataFromFD(const char *path,
int fd,
int format)
{
return virStorageFileGetMetadataInternal(path, fd, NULL, format);
}
/* Recursive workhorse for virStorageFileGetMetadata. */
static virStorageFileMetadataPtr
virStorageFileGetMetadataRecurse(const char *path, const char *directory,
int format, uid_t uid, gid_t gid,
bool allow_probe, virHashTablePtr cycle)
{
int fd;
VIR_DEBUG("path=%s format=%d uid=%d gid=%d probe=%d",
path, format, (int)uid, (int)gid, allow_probe);
virStorageFileMetadataPtr ret = NULL;
if (virHashLookup(cycle, path)) {
virReportError(VIR_ERR_INTERNAL_ERROR,
_("backing store for %s is self-referential"),
path);
return NULL;
}
if (virHashAddEntry(cycle, path, (void *)1) < 0)
return NULL;
if ((fd = virFileOpenAs(path, O_RDONLY, 0, uid, gid, 0)) < 0) {
virReportSystemError(-fd, _("cannot open file '%s'"), path);
return NULL;
}
ret = virStorageFileGetMetadataInternal(path, fd, directory, format);
if (VIR_CLOSE(fd) < 0)
VIR_WARN("could not close file %s", path);
if (ret && ret->backingStoreIsFile) {
if (ret->backingStoreFormat == VIR_STORAGE_FILE_AUTO && !allow_probe)
ret->backingStoreFormat = VIR_STORAGE_FILE_RAW;
else if (ret->backingStoreFormat == VIR_STORAGE_FILE_AUTO_SAFE)
ret->backingStoreFormat = VIR_STORAGE_FILE_AUTO;
format = ret->backingStoreFormat;
ret->backingMeta = virStorageFileGetMetadataRecurse(ret->backingStore,
ret->directory,
format,
uid, gid,
allow_probe,
cycle);
}
return ret;
}
/**
* virStorageFileGetMetadata:
*
* Extract metadata about the storage volume with the specified
* image format. If image format is VIR_STORAGE_FILE_AUTO, it
* will probe to automatically identify the format. Recurses through
* the entire chain.
*
* Open files using UID and GID (or pass -1 for the current user/group).
* Treat any backing files without explicit type as raw, unless ALLOW_PROBE.
*
* Callers are advised never to use VIR_STORAGE_FILE_AUTO as a
* format, since a malicious guest can turn a raw file into any
* other non-raw format at will.
*
* If the returned meta.backingStoreFormat is VIR_STORAGE_FILE_AUTO
* it indicates the image didn't specify an explicit format for its
* backing store. Callers are advised against using ALLOW_PROBE, as
* it would probe the backing store format in this case.
*
* Caller MUST free result after use via virStorageFileFreeMetadata.
*/
virStorageFileMetadataPtr
virStorageFileGetMetadata(const char *path, int format,
uid_t uid, gid_t gid,
bool allow_probe)
{
VIR_DEBUG("path=%s format=%d uid=%d gid=%d probe=%d",
path, format, (int)uid, (int)gid, allow_probe);
virHashTablePtr cycle = virHashCreate(5, NULL);
virStorageFileMetadataPtr ret;
if (!cycle)
return NULL;
if (format <= VIR_STORAGE_FILE_NONE)
format = allow_probe ? VIR_STORAGE_FILE_AUTO : VIR_STORAGE_FILE_RAW;
ret = virStorageFileGetMetadataRecurse(path, NULL, format, uid, gid,
allow_probe, cycle);
virHashFree(cycle);
return ret;
}
/**
* virStorageFileFreeMetadata:
*
* Free pointers in passed structure and structure itself.
*/
void
virStorageFileFreeMetadata(virStorageFileMetadata *meta)
{
if (!meta)
return;
virStorageFileFreeMetadata(meta->backingMeta);
VIR_FREE(meta->backingStore);
VIR_FREE(meta->backingStoreRaw);
VIR_FREE(meta->directory);
VIR_FREE(meta);
}
/**
* virStorageFileResize:
*
* Change the capacity of the raw storage file at 'path'.
*/
int
virStorageFileResize(const char *path, unsigned long long capacity)
{
int fd = -1;
int ret = -1;
if ((fd = open(path, O_RDWR)) < 0) {
virReportSystemError(errno, _("Unable to open '%s'"), path);
goto cleanup;
}
if (ftruncate(fd, capacity) < 0) {
virReportSystemError(errno, _("Failed to truncate file '%s'"), path);
goto cleanup;
}
if (VIR_CLOSE(fd) < 0) {
virReportSystemError(errno, _("Unable to save '%s'"), path);
goto cleanup;
}
ret = 0;
cleanup:
VIR_FORCE_CLOSE(fd);
return ret;
}
#ifdef __linux__
# ifndef NFS_SUPER_MAGIC
# define NFS_SUPER_MAGIC 0x6969
# endif
# ifndef OCFS2_SUPER_MAGIC
# define OCFS2_SUPER_MAGIC 0x7461636f
# endif
# ifndef GFS2_MAGIC
# define GFS2_MAGIC 0x01161970
# endif
# ifndef AFS_FS_MAGIC
# define AFS_FS_MAGIC 0x6B414653
# endif
int virStorageFileIsSharedFSType(const char *path,
int fstypes)
{
char *dirpath, *p;
struct statfs sb;
int statfs_ret;
if ((dirpath = strdup(path)) == NULL) {
virReportOOMError();
return -1;
}
do {
/* Try less and less of the path until we get to a
* directory we can stat. Even if we don't have 'x'
* permission on any directory in the path on the NFS
* server (assuming it's NFS), we will be able to stat the
* mount point, and that will properly tell us if the
* fstype is NFS.
*/
if ((p = strrchr(dirpath, '/')) == NULL) {
virReportSystemError(EINVAL,
_("Invalid relative path '%s'"), path);
VIR_FREE(dirpath);
return -1;
}
if (p == dirpath)
*(p+1) = '\0';
else
*p = '\0';
statfs_ret = statfs(dirpath, &sb);
} while ((statfs_ret < 0) && (p != dirpath));
VIR_FREE(dirpath);
if (statfs_ret < 0) {
virReportSystemError(errno,
_("cannot determine filesystem for '%s'"),
path);
return -1;
}
VIR_DEBUG("Check if path %s with FS magic %lld is shared",
path, (long long int)sb.f_type);
if ((fstypes & VIR_STORAGE_FILE_SHFS_NFS) &&
(sb.f_type == NFS_SUPER_MAGIC))
return 1;
if ((fstypes & VIR_STORAGE_FILE_SHFS_GFS2) &&
(sb.f_type == GFS2_MAGIC))
return 1;
if ((fstypes & VIR_STORAGE_FILE_SHFS_OCFS) &&
(sb.f_type == OCFS2_SUPER_MAGIC))
return 1;
if ((fstypes & VIR_STORAGE_FILE_SHFS_AFS) &&
(sb.f_type == AFS_FS_MAGIC))
return 1;
return 0;
}
#else
int virStorageFileIsSharedFSType(const char *path ATTRIBUTE_UNUSED,
int fstypes ATTRIBUTE_UNUSED)
{
/* XXX implement me :-) */
return 0;
}
#endif
int virStorageFileIsSharedFS(const char *path)
{
return virStorageFileIsSharedFSType(path,
VIR_STORAGE_FILE_SHFS_NFS |
VIR_STORAGE_FILE_SHFS_GFS2 |
VIR_STORAGE_FILE_SHFS_OCFS |
VIR_STORAGE_FILE_SHFS_AFS);
}
int virStorageFileIsClusterFS(const char *path)
{
/* These are coherent cluster filesystems known to be safe for
* migration with cache != none
*/
return virStorageFileIsSharedFSType(path,
VIR_STORAGE_FILE_SHFS_GFS2 |
VIR_STORAGE_FILE_SHFS_OCFS);
}
#ifdef LVS
int virStorageFileGetLVMKey(const char *path,
char **key)
{
/*
* # lvs --noheadings --unbuffered --nosuffix --options "uuid" LVNAME
* 06UgP5-2rhb-w3Bo-3mdR-WeoL-pytO-SAa2ky
*/
int status;
virCommandPtr cmd = virCommandNewArgList(
LVS,
"--noheadings", "--unbuffered", "--nosuffix",
"--options", "uuid", path,
NULL
);
int ret = -1;
*key = NULL;
/* Run the program and capture its output */
virCommandSetOutputBuffer(cmd, key);
if (virCommandRun(cmd, &status) < 0)
goto cleanup;
/* Explicitly check status == 0, rather than passing NULL
* to virCommandRun because we don't want to raise an actual
* error in this scenario, just return a NULL key.
*/
if (status == 0 && *key) {
char *nl;
char *tmp = *key;
/* Find first non-space character */
while (*tmp && c_isspace(*tmp)) {
tmp++;
}
/* Kill leading spaces */
if (tmp != *key)
memmove(*key, tmp, strlen(tmp)+1);
/* Kill trailing newline */
if ((nl = strchr(*key, '\n')))
*nl = '\0';
}
ret = 0;
cleanup:
if (*key && STREQ(*key, ""))
VIR_FREE(*key);
virCommandFree(cmd);
return ret;
}
#else
int virStorageFileGetLVMKey(const char *path,
char **key ATTRIBUTE_UNUSED)
{
virReportSystemError(ENOSYS, _("Unable to get LVM key for %s"), path);
return -1;
}
#endif
#ifdef WITH_UDEV
int virStorageFileGetSCSIKey(const char *path,
char **key)
{
int status;
virCommandPtr cmd = virCommandNewArgList(
"/lib/udev/scsi_id",
"--replace-whitespace",
"--whitelisted",
"--device", path,
NULL
);
int ret = -1;
*key = NULL;
/* Run the program and capture its output */
virCommandSetOutputBuffer(cmd, key);
if (virCommandRun(cmd, &status) < 0)
goto cleanup;
/* Explicitly check status == 0, rather than passing NULL
* to virCommandRun because we don't want to raise an actual
* error in this scenario, just return a NULL key.
*/
if (status == 0 && *key) {
char *nl = strchr(*key, '\n');
if (nl)
*nl = '\0';
}
ret = 0;
cleanup:
if (*key && STREQ(*key, ""))
VIR_FREE(*key);
virCommandFree(cmd);
return ret;
}
#else
int virStorageFileGetSCSIKey(const char *path,
char **key ATTRIBUTE_UNUSED)
{
virReportSystemError(ENOSYS, _("Unable to get SCSI key for %s"), path);
return -1;
}
#endif
/* Given a CHAIN that starts at the named file START, return a string
* pointing to either START or within CHAIN that gives the preferred
* name for the backing file NAME within that chain. Pass NULL for
* NAME to find the base of the chain. If META is not NULL, set *META
* to the point in the chain that describes NAME (or to NULL if the
* backing element is not a file). If PARENT is not NULL, set *PARENT
* to the preferred name of the parent (or to NULL if NAME matches
* START). Since the results point within CHAIN, they must not be
* independently freed. */
const char *
virStorageFileChainLookup(virStorageFileMetadataPtr chain, const char *start,
const char *name, virStorageFileMetadataPtr *meta,
const char **parent)
{
virStorageFileMetadataPtr owner;
const char *tmp;
if (!parent)
parent = &tmp;
*parent = NULL;
if (name ? STREQ(start, name) || virFileLinkPointsTo(start, name) :
!chain->backingStore) {
if (meta)
*meta = chain;
return start;
}
owner = chain;
*parent = start;
while (owner) {
if (!owner->backingStore)
goto error;
if (!name) {
if (!owner->backingMeta ||
!owner->backingMeta->backingStore)
break;
} else if (STREQ_NULLABLE(name, owner->backingStoreRaw) ||
STREQ(name, owner->backingStore)) {
break;
} else if (owner->backingStoreIsFile) {
char *absName = NULL;
if (virFindBackingFile(owner->directory, true, name,
NULL, &absName) < 0)
goto error;
if (absName && STREQ(absName, owner->backingStore)) {
VIR_FREE(absName);
break;
}
VIR_FREE(absName);
}
*parent = owner->backingStore;
owner = owner->backingMeta;
}
if (!owner)
goto error;
if (meta)
*meta = owner->backingMeta;
return owner->backingStore;
error:
*parent = NULL;
if (meta)
*meta = NULL;
return NULL;
}
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