Re: [PATCH v2 7/9] vdpa: solidrun: Fix potential UB bug with devres

Michael S. Tsirkin
2024-08-21T12:13:08Z

On Wed, Aug 21, 2024 at 09:18:40AM +0200, Philipp Stanner wrote:
> In psnet_open_pf_bar() a string later passed to pcim_iomap_regions() is
> placed on the stack. Neither pcim_iomap_regions() nor the functions it
> calls copy that string.
>
> Should the string later ever be used, this, consequently, causes
> undefined behavior since the stack frame will by then have disappeared.
>
> Fix the bug by allocating the string on the heap through
> devm_kasprintf().
>
> Cc: stable@vger.kernel.org # v6.3
> Fixes: 51a8f9d7f587 ("virtio: vdpa: new SolidNET DPU driver.")
> Reported-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> Closes: https://lore.kernel.org/all/74e9109a-ac59-49e2-9b1d-d825c9c9f891@wanadoo.fr/
> Suggested-by: Andy Shevchenko <andy@kernel.org>
> Signed-off-by: Philipp Stanner <pstanner@redhat.com>

I don't get why is this a part of a cleanup series -
looks like an unrelated bugfix?

> ---
> drivers/vdpa/solidrun/snet_main.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vdpa/solidrun/snet_main.c b/drivers/vdpa/solidrun/snet_main.c
> index 99428a04068d..4d42a05d70fc 100644
> --- a/drivers/vdpa/solidrun/snet_main.c
> +++ b/drivers/vdpa/solidrun/snet_main.c
> @@ -555,7 +555,7 @@ static const struct vdpa_config_ops snet_config_ops = {
>
> static int psnet_open_pf_bar(struct pci_dev *pdev, struct psnet *psnet)
> {
> - char name[50];
> + char *name;
> int ret, i, mask = 0;
> /* We don't know which BAR will be used to communicate..
> * We will map every bar with len > 0.
> @@ -573,7 +573,10 @@ static int psnet_open_pf_bar(struct pci_dev *pdev, struct psnet *psnet)
> return -ENODEV;
> }
>
> - snprintf(name, sizeof(name), "psnet[%s]-bars", pci_name(pdev));
> + name = devm_kasprintf(&pdev->dev, GFP_KERNEL, "psnet[%s]-bars", pci_name(pdev));
> + if (!name)
> + return -ENOMEM;
> +
> ret = pcim_iomap_regions(pdev, mask, name);
> if (ret) {
> SNET_ERR(pdev, "Failed to request and map PCI BARs\n");
> --
> 2.46.0