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block/cloop: refuse images with huge offsets arrays (CVE-2014-0144)

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Limit offsets_size to 512 MB so that:

1. g_malloc() does not abort due to an unreasonable size argument.

2. offsets_size does not overflow the bdrv_pread() int size argument.

This limit imposes a maximum image size of 16 TB at 256 KB block size.

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 13:05:27 +01:00
parent 509a41bab5
commit 7b103b36d6
3 changed files with 19 additions and 0 deletions
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9
block/cloop.c
View File

@ -107,6 +107,15 @@ static int cloop_open(BlockDriverState *bs, QDict *options, int flags,
return -EINVAL;
}
offsets_size = s->n_blocks * sizeof(uint64_t);
if (offsets_size > 512 * 1024 * 1024) {
/* Prevent ridiculous offsets_size which causes memory allocation to
* fail or overflows bdrv_pread() size. In practice the 512 MB
* offsets[] limit supports 16 TB images at 256 KB block size.
*/
error_setg(errp, "image requires too many offsets, "
"try increasing block size");
return -EINVAL;
}
s->offsets = g_malloc(offsets_size);
ret = bdrv_pread(bs->file, 128 + 4 + 4, s->offsets, offsets_size);

6
tests/qemu-iotests/075
View File

@ -74,6 +74,12 @@ _use_sample_img simple-pattern.cloop.bz2
poke_file "$TEST_IMG" "$n_blocks_offset" "\xff\xff\xff\xff"
$QEMU_IO -c "read 0 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir
echo
echo "== refuse images that require too many offsets ==="
_use_sample_img simple-pattern.cloop.bz2
poke_file "$TEST_IMG" "$n_blocks_offset" "\x04\x00\x00\x01"
$QEMU_IO -c "read 0 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir
# success, all done
echo "*** done"
rm -f $seq.full

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

@ -19,4 +19,8 @@ no file open, try 'help open'
== offsets_size overflow ===
qemu-io: can't open device TEST_DIR/simple-pattern.cloop: n_blocks 4294967295 must be 536870911 or less
no file open, try 'help open'
== refuse images that require too many offsets ===
qemu-io: can't open device TEST_DIR/simple-pattern.cloop: image requires too many offsets, try increasing block size
no file open, try 'help open'
*** done