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block: Catch integer overflow in bdrv_rw_co()

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Insanely large requests could cause an integer overflow in
bdrv_rw_co() while converting sectors to bytes. This patch catches the
problem and returns an error (if we hadn't overflown the integer here,
bdrv_check_byte_request() would have rejected the request, so we're not
breaking anything that was supposed to work before).

We actually do have a test case that triggers behaviour where we
accidentally let such a request pass, so that it would return success,
but read 0 bytes instead of the requested 4 GB. It fails now like it
should.

If the vdi block driver wants to be able to deal with huge images, it
can't read the whole block bitmap at once into memory like it does
today, but needs to use a metadata cache like qcow2 does.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2014-04-14 15:39:36 +02:00
parent 1dd3a44753
commit da15ee5134
2 changed files with 5 additions and 4 deletions
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4
block.c
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@ -2690,6 +2690,10 @@ static int bdrv_rw_co(BlockDriverState *bs, int64_t sector_num, uint8_t *buf,
.iov_len = nb_sectors * BDRV_SECTOR_SIZE,
};
if (nb_sectors < 0 || nb_sectors > INT_MAX / BDRV_SECTOR_SIZE) {
return -EINVAL;
}
qemu_iovec_init_external(&qiov, &iov, 1);
return bdrv_prwv_co(bs, sector_num << BDRV_SECTOR_BITS,
&qiov, is_write, flags);

5
tests/qemu-iotests/084.out
View File

@ -4,10 +4,7 @@ QA output created by 084
Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
Test 1: Maximum size (1024 TB):
image: TEST_DIR/t.IMGFMT
file format: IMGFMT
virtual size: 1024T (1125899905794048 bytes)
cluster_size: 1048576
qemu-img: Could not open 'TEST_DIR/t.IMGFMT': Could not open 'TEST_DIR/t.IMGFMT': Invalid argument
Test 2: Size too large (1024TB + 1)
qemu-img: Could not open 'TEST_DIR/t.IMGFMT': Unsupported VDI image size (size is 0x3fffffff10000, max supported is 0x3fffffff00000)