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util/iov: make qemu_iovec_init_extended() honest 

Actually, we can't extend the io vector in all cases. Handle possible
MAX_IOV and size_t overflows.

For now add assertion to callers (actually they rely on success anyway)
and fix them in the following patch.

Add also some additional good assertions to qemu_iovec_init_slice()
while being here.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20201211183934.169161-3-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2020-12-11 21:39:20 +03:00 committed by Eric Blake
parent 69b55e03f7
commit 4c002cef0e
3 changed files with 31 additions and 6 deletions
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10
block/io.c
View File

@ -1680,13 +1680,17 @@ static bool bdrv_pad_request(BlockDriverState *bs,
int64_t *offset, unsigned int *bytes,
BdrvRequestPadding *pad)
{
int ret;
if (!bdrv_init_padding(bs, *offset, *bytes, pad)) {
return false;
}
qemu_iovec_init_extended(&pad->local_qiov, pad->buf, pad->head,
*qiov, *qiov_offset, *bytes,
pad->buf + pad->buf_len - pad->tail, pad->tail);
ret = qemu_iovec_init_extended(&pad->local_qiov, pad->buf, pad->head,
*qiov, *qiov_offset, *bytes,
pad->buf + pad->buf_len - pad->tail,
pad->tail);
assert(ret == 0);
*bytes += pad->head + pad->tail;
*offset -= pad->head;
*qiov = &pad->local_qiov;

2
include/qemu/iov.h
View File

@ -222,7 +222,7 @@ static inline void *qemu_iovec_buf(QEMUIOVector *qiov)
void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint);
void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov);
void qemu_iovec_init_extended(
int qemu_iovec_init_extended(
QEMUIOVector *qiov,
void *head_buf, size_t head_len,
QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len,

25
util/iov.c
View File

@ -415,7 +415,7 @@ int qemu_iovec_subvec_niov(QEMUIOVector *qiov, size_t offset, size_t len)
* Compile new iovec, combining @head_buf buffer, sub-qiov of @mid_qiov,
* and @tail_buf buffer into new qiov.
*/
void qemu_iovec_init_extended(
int qemu_iovec_init_extended(
QEMUIOVector *qiov,
void *head_buf, size_t head_len,
QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len,
@ -425,12 +425,24 @@ void qemu_iovec_init_extended(
int total_niov, mid_niov = 0;
struct iovec *p, *mid_iov = NULL;
assert(mid_qiov->niov <= IOV_MAX);
if (SIZE_MAX - head_len < mid_len ||
SIZE_MAX - head_len - mid_len < tail_len)
{
return -EINVAL;
}
if (mid_len) {
mid_iov = qiov_slice(mid_qiov, mid_offset, mid_len,
&mid_head, &mid_tail, &mid_niov);
}
total_niov = !!head_len + mid_niov + !!tail_len;
if (total_niov > IOV_MAX) {
return -EINVAL;
}
if (total_niov == 1) {
qemu_iovec_init_buf(qiov, NULL, 0);
p = &qiov->local_iov;
@ -459,6 +471,8 @@ void qemu_iovec_init_extended(
p->iov_base = tail_buf;
p->iov_len = tail_len;
}
return 0;
}
/*
@ -492,7 +506,14 @@ bool qemu_iovec_is_zero(QEMUIOVector *qiov, size_t offset, size_t bytes)
void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
size_t offset, size_t len)
{
qemu_iovec_init_extended(qiov, NULL, 0, source, offset, len, NULL, 0);
int ret;
assert(source->size >= len);
assert(source->size - len >= offset);
/* We shrink the request, so we can't overflow neither size_t nor MAX_IOV */
ret = qemu_iovec_init_extended(qiov, NULL, 0, source, offset, len, NULL, 0);
assert(ret == 0);
}
void qemu_iovec_destroy(QEMUIOVector *qiov)