xemu-project/xemu
1
0
Fork 0
mirror of https://github.com/xemu-project/xemu.git synced 2024-11-27 05:20:50 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

qcow2: avoid misaligned 64bit bswap

Browse Source 
If we create a buffer directly on the stack by using 12 bytes, there's
no guarantee the 64bit value we want to swap will be aligned, which
could cause errors with undefined behavior.

Spotted with clang -fsanitize=undefined and observed in iotests 15, 26,
44, 115 and 121.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
John Snow 2015-11-02 18:32:06 -05:00 committed by Kevin Wolf
parent bcdce5a73c
commit 9533423063
1 changed files with 7 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
block/qcow2-refcount.c
View File

@ -560,13 +560,16 @@ static int alloc_refcount_block(BlockDriverState *bs,
}
/* Hook up the new refcount table in the qcow2 header */
uint8_t data[12];
cpu_to_be64w((uint64_t*)data, table_offset);
cpu_to_be32w((uint32_t*)(data + 8), table_clusters);
struct QEMU_PACKED {
uint64_t d64;
uint32_t d32;
} data;
cpu_to_be64w(&data.d64, table_offset);
cpu_to_be32w(&data.d32, table_clusters);
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_ALLOC_SWITCH_TABLE);
ret = bdrv_pwrite_sync(bs->file->bs,
offsetof(QCowHeader, refcount_table_offset),
data, sizeof(data));
&data, sizeof(data));
if (ret < 0) {
goto fail_table;
}