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block/cloop: fix offsets[] size off-by-one 

cloop stores the number of compressed blocks in the n_blocks header
field.  The file actually contains n_blocks + 1 offsets, where the extra
offset is the end-of-file offset.

The following line in cloop_read_block() results in an out-of-bounds
offsets[] access:

    uint32_t bytes = s->offsets[block_num + 1] - s->offsets[block_num];

This patch allocates and loads the extra offset so that
cloop_read_block() works correctly when the last block is accessed.

Notice that we must free s->offsets[] unconditionally now since there is
always an end-of-file offset.

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>
This commit is contained in:
Stefan Hajnoczi 2014-03-26 13:05:29 +01:00
parent f56b9bc3ae
commit 42d43d35d9
3 changed files with 14 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
block/cloop.c
View File

@ -99,14 +99,14 @@ static int cloop_open(BlockDriverState *bs, QDict *options, int flags,
s->n_blocks = be32_to_cpu(s->n_blocks); s->n_blocks = be32_to_cpu(s->n_blocks);
/* read offsets */ /* read offsets */
if (s->n_blocks > UINT32_MAX / sizeof(uint64_t)) { if (s->n_blocks > (UINT32_MAX - 1) / sizeof(uint64_t)) {
/* Prevent integer overflow */ /* Prevent integer overflow */
error_setg(errp, "n_blocks %u must be %zu or less", error_setg(errp, "n_blocks %u must be %zu or less",
s->n_blocks, s->n_blocks,
UINT32_MAX / sizeof(uint64_t)); (UINT32_MAX - 1) / sizeof(uint64_t));
return -EINVAL; return -EINVAL;
} }
offsets_size = s->n_blocks * sizeof(uint64_t); offsets_size = (s->n_blocks + 1) * sizeof(uint64_t);
if (offsets_size > 512 * 1024 * 1024) { if (offsets_size > 512 * 1024 * 1024) {
/* Prevent ridiculous offsets_size which causes memory allocation to /* Prevent ridiculous offsets_size which causes memory allocation to
* fail or overflows bdrv_pread() size. In practice the 512 MB * fail or overflows bdrv_pread() size. In practice the 512 MB
@ -123,7 +123,7 @@ static int cloop_open(BlockDriverState *bs, QDict *options, int flags,
goto fail; goto fail;
} }
for(i=0;i<s->n_blocks;i++) { for (i = 0; i < s->n_blocks + 1; i++) {
uint64_t size; uint64_t size;
s->offsets[i] = be64_to_cpu(s->offsets[i]); s->offsets[i] = be64_to_cpu(s->offsets[i]);
@ -243,9 +243,7 @@ static coroutine_fn int cloop_co_read(BlockDriverState *bs, int64_t sector_num,
static void cloop_close(BlockDriverState *bs) static void cloop_close(BlockDriverState *bs)
{ {
BDRVCloopState *s = bs->opaque; BDRVCloopState *s = bs->opaque;
if (s->n_blocks > 0) { g_free(s->offsets);
g_free(s->offsets);
}
g_free(s->compressed_block); g_free(s->compressed_block);
g_free(s->uncompressed_block); g_free(s->uncompressed_block);
inflateEnd(&s->zstream); inflateEnd(&s->zstream);

5
tests/qemu-iotests/075
View File

@ -51,6 +51,11 @@ echo "== check that the first sector can be read =="
_use_sample_img simple-pattern.cloop.bz2 _use_sample_img simple-pattern.cloop.bz2
$QEMU_IO -c "read 0 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir $QEMU_IO -c "read 0 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir
echo
echo "== check that the last sector can be read =="
_use_sample_img simple-pattern.cloop.bz2
$QEMU_IO -c "read $((1024 * 1024 - 512)) 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir
echo echo
echo "== block_size must be a multiple of 512 ==" echo "== block_size must be a multiple of 512 =="
_use_sample_img simple-pattern.cloop.bz2 _use_sample_img simple-pattern.cloop.bz2

4
tests/qemu-iotests/075.out
View File

@ -4,6 +4,10 @@ QA output created by 075
read 512/512 bytes at offset 0 read 512/512 bytes at offset 0
512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
== check that the last sector can be read ==
read 512/512 bytes at offset 1048064
512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
== block_size must be a multiple of 512 == == block_size must be a multiple of 512 ==
qemu-io: can't open device TEST_DIR/simple-pattern.cloop: block_size 513 must be a multiple of 512 qemu-io: can't open device TEST_DIR/simple-pattern.cloop: block_size 513 must be a multiple of 512
no file open, try 'help open' no file open, try 'help open'