On 05/11/2018 07:08 AM, Fam Zheng wrote:
We don't verify the request range against s->size in the I/O callbacks
except for raw_co_pwritev. This is wrong (especially for
raw_co_pwrite_zeroes and raw_co_pdiscard), so fix them.
Did you bother identifying how long the bug has been present (but read
below, because I'm not sure there was even a bug)?
CC: qemu-sta...@nongnu.org
Signed-off-by: Fam Zheng <f...@redhat.com>
---
block/raw-format.c | 63 ++++++++++++++++++++++++++++++++----------------------
1 file changed, 38 insertions(+), 25 deletions(-)
diff --git a/block/raw-format.c b/block/raw-format.c
index a378547c99..803083f1a1 100644
--- a/block/raw-format.c
+++ b/block/raw-format.c
@@ -167,16 +167,36 @@ static void raw_reopen_abort(BDRVReopenState *state)
state->opaque = NULL;
}
+/* Check and adjust the offset, against 'offset' and 'size' options. */
+static inline int raw_adjust_offset(BlockDriverState *bs, uint64_t *offset,
+ uint64_t bytes)
+{
+ BDRVRawState *s = bs->opaque;
+
+ if (s->has_size && (*offset > s->size || bytes > (s->size - *offset))) {
+ /* There's not enough space for the data. Don't write anything and just
+ * fail to prevent leaking out of the size specified in options. */
+ return -ENOSPC;
+ }
Can this even trigger? The block layer should already be clamping
requests according to the device's reported size, and we already report
a smaller size according to s->size and s->offset. This could probably
be an assertion instead.
+
+ if (*offset > UINT64_MAX - s->offset) {
+ return -EINVAL;
Should this be against INT64_MAX instead? After all, we really do use
off_t (a 63-bit quantity, since it is signed), rather than uint64_t, as
our maximum (theoretical) image size. But again, can it even trigger,
or can it be an assertion?
+ }
+ *offset += s->offset;
+
+ return 0;
+}
+
static int coroutine_fn raw_co_preadv(BlockDriverState *bs, uint64_t offset,
uint64_t bytes, QEMUIOVector *qiov,
int flags)
{
- BDRVRawState *s = bs->opaque;
+ int ret;
- if (offset > UINT64_MAX - s->offset) {
- return -EINVAL;
+ ret = raw_adjust_offset(bs, &offset, bytes);
If I'm right and we can assert instead of failing, then
raw_adjust_offset() doesn't return failure. If I'm wrong, then there is
now a code path where we can return ENOSPC on a read, which is unusual
and probably wrong.
+ if (ret) {
+ return ret;
}
- offset += s->offset;
BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags);
@@ -186,23 +206,11 @@ static int coroutine_fn raw_co_pwritev(BlockDriverState
*bs, uint64_t offset,
uint64_t bytes, QEMUIOVector *qiov,
int flags)
{
- BDRVRawState *s = bs->opaque;
void *buf = NULL;
BlockDriver *drv;
QEMUIOVector local_qiov;
int ret;
- if (s->has_size && (offset > s->size || bytes > (s->size - offset))) {
- /* There's not enough space for the data. Don't write anything and just
- * fail to prevent leaking out of the size specified in options. */
- return -ENOSPC;
- }
-
- if (offset > UINT64_MAX - s->offset) {
- ret = -EINVAL;
- goto fail;
- }
Okay, so you're just doing code refactoring; perhaps we could have done
assertions here.
-
if (bs->probed && offset < BLOCK_PROBE_BUF_SIZE && bytes) {
/* Handling partial writes would be a pain - so we just
* require that guests have 512-byte request alignment if
@@ -237,7 +245,10 @@ static int coroutine_fn raw_co_pwritev(BlockDriverState
*bs, uint64_t offset,
qiov = &local_qiov;
}
- offset += s->offset;
+ ret = raw_adjust_offset(bs, &offset, bytes);
+ if (ret) {
+ goto fail;
+ }
BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO);
ret = bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);
@@ -267,22 +278,24 @@ static int coroutine_fn
raw_co_pwrite_zeroes(BlockDriverState *bs,
int64_t offset, int bytes,
BdrvRequestFlags flags)
{
- BDRVRawState *s = bs->opaque;
- if (offset > UINT64_MAX - s->offset) {
- return -EINVAL;
+ int ret;
+
+ ret = raw_adjust_offset(bs, (uint64_t *)&offset, bytes);
+ if (ret) {
+ return ret;
}
- offset += s->offset;
If I'm right and raw_adjust_offset() can't fail, then this didn't add
any protection. If I'm wrong and it is possible to get the block layer
to send a request beyond our advertised size, then this is indeed a bug
fix worthy of being on the stable branch.
return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
}
static int coroutine_fn raw_co_pdiscard(BlockDriverState *bs,
int64_t offset, int bytes)
{
- BDRVRawState *s = bs->opaque;
- if (offset > UINT64_MAX - s->offset) {
- return -EINVAL;
+ int ret;
+
+ ret = raw_adjust_offset(bs, (uint64_t *)&offset, bytes);
+ if (ret) {
+ return ret;
}
- offset += s->offset;
return bdrv_co_pdiscard(bs->file->bs, offset, bytes);
}
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
