[PATCH v2 3/3] vhost: fix mmap error check in VDUSE IOTLB miss handler

[Chenbo Xia]

> On Jan 14, 2026, at 23:34, Maxime Coquelin <maxime.coquelin at redhat.com> wrote:
> 
> External email: Use caution opening links or attachments
> 
> 
> The mmap() function returns MAP_FAILED on failure, not NULL.
> The current check for !mmap_addr will never detect mmap failures.
> 
> When mmap fails but the error is not detected, an invalid address (-1)
> is inserted into the IOTLB cache via vhost_user_iotlb_cache_insert().
> Subsequent attempts to access this address will cause memory
> corruption or crash.
> 
> Fix by checking for MAP_FAILED instead of NULL. Also add strerror to
> the error message for easier debugging.
> 
> Fixes: f27d5206c598 ("vhost: add VDUSE callback for IOTLB miss")
> Cc: stable at dpdk.org
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
> Reviewed-by: David Marchand <david.marchand at redhat.com>
> ---
> lib/vhost/vduse.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/vhost/vduse.c b/lib/vhost/vduse.c
> index 897dee9f1b..0b5d158fee 100644
> --- a/lib/vhost/vduse.c
> +++ b/lib/vhost/vduse.c
> @@ -86,9 +86,10 @@ vduse_iotlb_miss(struct virtio_net *dev, uint64_t iova, uint8_t perm __rte_unuse
> 
>        size = entry.last - entry.start + 1;
>        mmap_addr = mmap(0, size + entry.offset, entry.perm, MAP_SHARED, fd, 0);
> -       if (!mmap_addr) {
> +       if (mmap_addr == MAP_FAILED) {
>                VHOST_CONFIG_LOG(dev->ifname, ERR,
> -                               "Failed to mmap IOTLB entry for 0x%" PRIx64, iova);
> +                               "Failed to mmap IOTLB entry for 0x%" PRIx64 ": %s",
> +                               iova, strerror(errno));
>                ret = -1;
>                goto close_fd;
>        }
> —
> 2.52.0
> 

Reviewed-by: Chenbo Xia <chenbox at nvidia.com>