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net/tap: Avoid variable-length array

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Use a heap allocation instead of a variable length array in
tap_receive_iov().

The codebase has very few VLAs, and if we can get rid of them all we
can make the compiler error on new additions.  This is a defensive
measure against security bugs where an on-stack dynamic allocation
isn't correctly size-checked (e.g.  CVE-2021-3527).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Francisco Iglesias <frasse.iglesias@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
This commit is contained in:
Peter Maydell 2023-08-24 16:32:24 +01:00 committed by Jason Wang
parent c4cf68198e
commit 6d7a53e9f1
1 changed files with 2 additions and 1 deletions
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net/tap.c
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@ -118,10 +118,11 @@ static ssize_t tap_receive_iov(NetClientState *nc, const struct iovec *iov,
{
TAPState *s = DO_UPCAST(TAPState, nc, nc);
const struct iovec *iovp = iov;
struct iovec iov_copy[iovcnt + 1];
g_autofree struct iovec *iov_copy = NULL;
struct virtio_net_hdr_mrg_rxbuf hdr = { };
if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
iov_copy = g_new(struct iovec, iovcnt + 1);
iov_copy[0].iov_base = &hdr;
iov_copy[0].iov_len = s->host_vnet_hdr_len;
memcpy(&iov_copy[1], iov, iovcnt * sizeof(*iov));