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qemu-e2k/block/dmg.c
Stefan Hajnoczi f0dce23475 dmg: prevent chunk buffer overflow (CVE-2014-0145) 
Both compressed and uncompressed I/O is buffered.  dmg_open() calculates
the maximum buffer size needed from the metadata in the image file.

There is currently a buffer overflow since ->lengths[] is accounted
against the maximum compressed buffer size but actually uses the
uncompressed buffer:

  switch (s->types[chunk]) {
  case 1: /* copy */
      ret = bdrv_pread(bs->file, s->offsets[chunk],
                       s->uncompressed_chunk, s->lengths[chunk]);

We must account against the maximum uncompressed buffer size for type=1
chunks.

This patch fixes the maximum buffer size calculation to take into
account the chunk type.  It is critical that we update the correct
maximum since there are two buffers ->compressed_chunk and
->uncompressed_chunk.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-04-01 15:22:35 +02:00

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/*
* QEMU Block driver for DMG images
*
* Copyright (c) 2004 Johannes E. Schindelin
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu-common.h"
#include "block/block_int.h"
#include "qemu/bswap.h"
#include "qemu/module.h"
#include <zlib.h>
enum {
/* Limit chunk sizes to prevent unreasonable amounts of memory being used
* or truncating when converting to 32-bit types
*/
DMG_LENGTHS_MAX = 64 * 1024 * 1024, /* 64 MB */
DMG_SECTORCOUNTS_MAX = DMG_LENGTHS_MAX / 512,
};
typedef struct BDRVDMGState {
CoMutex lock;
/* each chunk contains a certain number of sectors,
* offsets[i] is the offset in the .dmg file,
* lengths[i] is the length of the compressed chunk,
* sectors[i] is the sector beginning at offsets[i],
* sectorcounts[i] is the number of sectors in that chunk,
* the sectors array is ordered
* 0<=i<n_chunks */
uint32_t n_chunks;
uint32_t* types;
uint64_t* offsets;
uint64_t* lengths;
uint64_t* sectors;
uint64_t* sectorcounts;
uint32_t current_chunk;
uint8_t *compressed_chunk;
uint8_t *uncompressed_chunk;
z_stream zstream;
} BDRVDMGState;
static int dmg_probe(const uint8_t *buf, int buf_size, const char *filename)
{
int len;
if (!filename) {
return 0;
}
len = strlen(filename);
if (len > 4 && !strcmp(filename + len - 4, ".dmg")) {
return 2;
}
return 0;
}
static int read_uint64(BlockDriverState *bs, int64_t offset, uint64_t *result)
{
uint64_t buffer;
int ret;
ret = bdrv_pread(bs->file, offset, &buffer, 8);
if (ret < 0) {
return ret;
}
*result = be64_to_cpu(buffer);
return 0;
}
static int read_uint32(BlockDriverState *bs, int64_t offset, uint32_t *result)
{
uint32_t buffer;
int ret;
ret = bdrv_pread(bs->file, offset, &buffer, 4);
if (ret < 0) {
return ret;
}
*result = be32_to_cpu(buffer);
return 0;
}
/* Increase max chunk sizes, if necessary. This function is used to calculate
* the buffer sizes needed for compressed/uncompressed chunk I/O.
*/
static void update_max_chunk_size(BDRVDMGState *s, uint32_t chunk,
uint32_t *max_compressed_size,
uint32_t *max_sectors_per_chunk)
{
uint32_t compressed_size = 0;
uint32_t uncompressed_sectors = 0;
switch (s->types[chunk]) {
case 0x80000005: /* zlib compressed */
compressed_size = s->lengths[chunk];
uncompressed_sectors = s->sectorcounts[chunk];
break;
case 1: /* copy */
uncompressed_sectors = (s->lengths[chunk] + 511) / 512;
break;
case 2: /* zero */
uncompressed_sectors = s->sectorcounts[chunk];
break;
}
if (compressed_size > *max_compressed_size) {
*max_compressed_size = compressed_size;
}
if (uncompressed_sectors > *max_sectors_per_chunk) {
*max_sectors_per_chunk = uncompressed_sectors;
}
}
static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
Error **errp)
{
BDRVDMGState *s = bs->opaque;
uint64_t info_begin, info_end, last_in_offset, last_out_offset;
uint32_t count, tmp;
uint32_t max_compressed_size = 1, max_sectors_per_chunk = 1, i;
int64_t offset;
int ret;
bs->read_only = 1;
s->n_chunks = 0;
s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL;
/* read offset of info blocks */
offset = bdrv_getlength(bs->file);
if (offset < 0) {
ret = offset;
goto fail;
}
offset -= 0x1d8;
ret = read_uint64(bs, offset, &info_begin);
if (ret < 0) {
goto fail;
} else if (info_begin == 0) {
ret = -EINVAL;
goto fail;
}
ret = read_uint32(bs, info_begin, &tmp);
if (ret < 0) {
goto fail;
} else if (tmp != 0x100) {
ret = -EINVAL;
goto fail;
}
ret = read_uint32(bs, info_begin + 4, &count);
if (ret < 0) {
goto fail;
} else if (count == 0) {
ret = -EINVAL;
goto fail;
}
info_end = info_begin + count;
offset = info_begin + 0x100;
/* read offsets */
last_in_offset = last_out_offset = 0;
while (offset < info_end) {
uint32_t type;
ret = read_uint32(bs, offset, &count);
if (ret < 0) {
goto fail;
} else if (count == 0) {
ret = -EINVAL;
goto fail;
}
offset += 4;
ret = read_uint32(bs, offset, &type);
if (ret < 0) {
goto fail;
}
if (type == 0x6d697368 && count >= 244) {
size_t new_size;
uint32_t chunk_count;
offset += 4;
offset += 200;
chunk_count = (count - 204) / 40;
new_size = sizeof(uint64_t) * (s->n_chunks + chunk_count);
s->types = g_realloc(s->types, new_size / 2);
s->offsets = g_realloc(s->offsets, new_size);
s->lengths = g_realloc(s->lengths, new_size);
s->sectors = g_realloc(s->sectors, new_size);
s->sectorcounts = g_realloc(s->sectorcounts, new_size);
for (i = s->n_chunks; i < s->n_chunks + chunk_count; i++) {
ret = read_uint32(bs, offset, &s->types[i]);
if (ret < 0) {
goto fail;
}
offset += 4;
if (s->types[i] != 0x80000005 && s->types[i] != 1 &&
s->types[i] != 2) {
if (s->types[i] == 0xffffffff && i > 0) {
last_in_offset = s->offsets[i - 1] + s->lengths[i - 1];
last_out_offset = s->sectors[i - 1] +
s->sectorcounts[i - 1];
}
chunk_count--;
i--;
offset += 36;
continue;
}
offset += 4;
ret = read_uint64(bs, offset, &s->sectors[i]);
if (ret < 0) {
goto fail;
}
s->sectors[i] += last_out_offset;
offset += 8;
ret = read_uint64(bs, offset, &s->sectorcounts[i]);
if (ret < 0) {
goto fail;
}
offset += 8;
if (s->sectorcounts[i] > DMG_SECTORCOUNTS_MAX) {
error_report("sector count %" PRIu64 " for chunk %u is "
"larger than max (%u)",
s->sectorcounts[i], i, DMG_SECTORCOUNTS_MAX);
ret = -EINVAL;
goto fail;
}
ret = read_uint64(bs, offset, &s->offsets[i]);
if (ret < 0) {
goto fail;
}
s->offsets[i] += last_in_offset;
offset += 8;
ret = read_uint64(bs, offset, &s->lengths[i]);
if (ret < 0) {
goto fail;
}
offset += 8;
if (s->lengths[i] > DMG_LENGTHS_MAX) {
error_report("length %" PRIu64 " for chunk %u is larger "
"than max (%u)",
s->lengths[i], i, DMG_LENGTHS_MAX);
ret = -EINVAL;
goto fail;
}
update_max_chunk_size(s, i, &max_compressed_size,
&max_sectors_per_chunk);
}
s->n_chunks += chunk_count;
}
}
/* initialize zlib engine */
s->compressed_chunk = g_malloc(max_compressed_size + 1);
s->uncompressed_chunk = g_malloc(512 * max_sectors_per_chunk);
if (inflateInit(&s->zstream) != Z_OK) {
ret = -EINVAL;
goto fail;
}
s->current_chunk = s->n_chunks;
qemu_co_mutex_init(&s->lock);
return 0;
fail:
g_free(s->types);
g_free(s->offsets);
g_free(s->lengths);
g_free(s->sectors);
g_free(s->sectorcounts);
g_free(s->compressed_chunk);
g_free(s->uncompressed_chunk);
return ret;
}
static inline int is_sector_in_chunk(BDRVDMGState* s,
uint32_t chunk_num, uint64_t sector_num)
{
if (chunk_num >= s->n_chunks || s->sectors[chunk_num] > sector_num ||
s->sectors[chunk_num] + s->sectorcounts[chunk_num] <= sector_num) {
return 0;
} else {
return -1;
}
}
static inline uint32_t search_chunk(BDRVDMGState *s, uint64_t sector_num)
{
/* binary search */
uint32_t chunk1 = 0, chunk2 = s->n_chunks, chunk3;
while (chunk1 != chunk2) {
chunk3 = (chunk1 + chunk2) / 2;
if (s->sectors[chunk3] > sector_num) {
chunk2 = chunk3;
} else if (s->sectors[chunk3] + s->sectorcounts[chunk3] > sector_num) {
return chunk3;
} else {
chunk1 = chunk3;
}
}
return s->n_chunks; /* error */
}
static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
{
BDRVDMGState *s = bs->opaque;
if (!is_sector_in_chunk(s, s->current_chunk, sector_num)) {
int ret;
uint32_t chunk = search_chunk(s, sector_num);
if (chunk >= s->n_chunks) {
return -1;
}
s->current_chunk = s->n_chunks;
switch (s->types[chunk]) {
case 0x80000005: { /* zlib compressed */
/* we need to buffer, because only the chunk as whole can be
* inflated. */
ret = bdrv_pread(bs->file, s->offsets[chunk],
s->compressed_chunk, s->lengths[chunk]);
if (ret != s->lengths[chunk]) {
return -1;
}
s->zstream.next_in = s->compressed_chunk;
s->zstream.avail_in = s->lengths[chunk];
s->zstream.next_out = s->uncompressed_chunk;
s->zstream.avail_out = 512 * s->sectorcounts[chunk];
ret = inflateReset(&s->zstream);
if (ret != Z_OK) {
return -1;
}
ret = inflate(&s->zstream, Z_FINISH);
if (ret != Z_STREAM_END ||
s->zstream.total_out != 512 * s->sectorcounts[chunk]) {
return -1;
}
break; }
case 1: /* copy */
ret = bdrv_pread(bs->file, s->offsets[chunk],
s->uncompressed_chunk, s->lengths[chunk]);
if (ret != s->lengths[chunk]) {
return -1;
}
break;
case 2: /* zero */
memset(s->uncompressed_chunk, 0, 512 * s->sectorcounts[chunk]);
break;
}
s->current_chunk = chunk;
}
return 0;
}
static int dmg_read(BlockDriverState *bs, int64_t sector_num,
uint8_t *buf, int nb_sectors)
{
BDRVDMGState *s = bs->opaque;
int i;
for (i = 0; i < nb_sectors; i++) {
uint32_t sector_offset_in_chunk;
if (dmg_read_chunk(bs, sector_num + i) != 0) {
return -1;
}
sector_offset_in_chunk = sector_num + i - s->sectors[s->current_chunk];
memcpy(buf + i * 512,
s->uncompressed_chunk + sector_offset_in_chunk * 512, 512);
}
return 0;
}
static coroutine_fn int dmg_co_read(BlockDriverState *bs, int64_t sector_num,
uint8_t *buf, int nb_sectors)
{
int ret;
BDRVDMGState *s = bs->opaque;
qemu_co_mutex_lock(&s->lock);
ret = dmg_read(bs, sector_num, buf, nb_sectors);
qemu_co_mutex_unlock(&s->lock);
return ret;
}
static void dmg_close(BlockDriverState *bs)
{
BDRVDMGState *s = bs->opaque;
g_free(s->types);
g_free(s->offsets);
g_free(s->lengths);
g_free(s->sectors);
g_free(s->sectorcounts);
g_free(s->compressed_chunk);
g_free(s->uncompressed_chunk);
inflateEnd(&s->zstream);
}
static BlockDriver bdrv_dmg = {
.format_name = "dmg",
.instance_size = sizeof(BDRVDMGState),
.bdrv_probe = dmg_probe,
.bdrv_open = dmg_open,
.bdrv_read = dmg_co_read,
.bdrv_close = dmg_close,
};
static void bdrv_dmg_init(void)
{
bdrv_register(&bdrv_dmg);
}
block_init(bdrv_dmg_init);
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