Re: [PATCH] scsi/lsi53c895a: restrict DMA engine to memory regions (CVE-2023-0330)

[Karl Heubaum]

Did this CVE fix fall in the cracks during the QEMU 8.0 merge window?

Karl

> On Jan 16, 2023, at 2:42 PM, Mauro Matteo Cascella <mcascell@redhat.com> 
> wrote:
> 
> This prevents the well known DMA-MMIO reentrancy problem (upstream issue #556)
> leading to memory corruption bugs like stack overflow or use-after-free.
> 
> Fixes: CVE-2023-0330
> Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
> Reported-by: Zheyu Ma <zheyuma97@gmail.com>
> ---
> hw/scsi/lsi53c895a.c               | 14 +++++++++----
> tests/qtest/fuzz-lsi53c895a-test.c | 32 ++++++++++++++++++++++++++++++
> 2 files changed, 42 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
> index af93557a9a..89c52594eb 100644
> --- a/hw/scsi/lsi53c895a.c
> +++ b/hw/scsi/lsi53c895a.c
> @@ -446,22 +446,28 @@ static void lsi_reselect(LSIState *s, lsi_request *p);
> static inline void lsi_mem_read(LSIState *s, dma_addr_t addr,
>                                void *buf, dma_addr_t len)
> {
> +    const MemTxAttrs attrs = { .memory = true };
> +
>     if (s->dmode & LSI_DMODE_SIOM) {
> -        address_space_read(&s->pci_io_as, addr, MEMTXATTRS_UNSPECIFIED,
> +        address_space_read(&s->pci_io_as, addr, attrs,
>                            buf, len);
>     } else {
> -        pci_dma_read(PCI_DEVICE(s), addr, buf, len);
> +        pci_dma_rw(PCI_DEVICE(s), addr, buf, len,
> +                      DMA_DIRECTION_TO_DEVICE, attrs);
>     }
> }
> 
> static inline void lsi_mem_write(LSIState *s, dma_addr_t addr,
>                                 const void *buf, dma_addr_t len)
> {
> +    const MemTxAttrs attrs = { .memory = true };
> +
>     if (s->dmode & LSI_DMODE_DIOM) {
> -        address_space_write(&s->pci_io_as, addr, MEMTXATTRS_UNSPECIFIED,
> +        address_space_write(&s->pci_io_as, addr, attrs,
>                             buf, len);
>     } else {
> -        pci_dma_write(PCI_DEVICE(s), addr, buf, len);
> +        pci_dma_rw(PCI_DEVICE(s), addr, (void *) buf, len,
> +                      DMA_DIRECTION_FROM_DEVICE, attrs);
>     }
> }
> 
> diff --git a/tests/qtest/fuzz-lsi53c895a-test.c 
> b/tests/qtest/fuzz-lsi53c895a-test.c
> index 392a7ae7ed..35c02e89f3 100644
> --- a/tests/qtest/fuzz-lsi53c895a-test.c
> +++ b/tests/qtest/fuzz-lsi53c895a-test.c
> @@ -8,6 +8,35 @@
> #include "qemu/osdep.h"
> #include "libqtest.h"
> 
> +/*
> + * This used to trigger a DMA reentrancy issue
> + * leading to memory corruption bugs like stack
> + * overflow or use-after-free
> + */
> +static void test_lsi_dma_reentrancy(void)
> +{
> +    QTestState *s;
> +
> +    s = qtest_init("-M q35 -m 512M -nodefaults "
> +                   "-blockdev driver=null-co,node-name=null0 "
> +                   "-device lsi53c810 -device scsi-cd,drive=null0");
> +
> +    qtest_outl(s, 0xcf8, 0x80000804); /* PCI Command Register */
> +    qtest_outw(s, 0xcfc, 0x7);        /* Enables accesses */
> +    qtest_outl(s, 0xcf8, 0x80000814); /* Memory Bar 1 */
> +    qtest_outl(s, 0xcfc, 0xff100000); /* Set MMIO Address*/
> +    qtest_outl(s, 0xcf8, 0x80000818); /* Memory Bar 2 */
> +    qtest_outl(s, 0xcfc, 0xff000000); /* Set RAM Address*/
> +    qtest_writel(s, 0xff000000, 0xc0000024);
> +    qtest_writel(s, 0xff000114, 0x00000080);
> +    qtest_writel(s, 0xff00012c, 0xff000000);
> +    qtest_writel(s, 0xff000004, 0xff000114);
> +    qtest_writel(s, 0xff000008, 0xff100014);
> +    qtest_writel(s, 0xff10002f, 0x000000ff);
> +
> +    qtest_quit(s);
> +}
> +
> /*
>  * This used to trigger a UAF in lsi_do_msgout()
>  * https://gitlab.com/qemu-project/qemu/-/issues/972
> @@ -120,5 +149,8 @@ int main(int argc, char **argv)
>     qtest_add_func("fuzz/lsi53c895a/lsi_do_msgout_cancel_req",
>                    test_lsi_do_msgout_cancel_req);
> 
> +    qtest_add_func("fuzz/lsi53c895a/lsi_dma_reentrancy",
> +                   test_lsi_dma_reentrancy);
> +
>     return g_test_run();
> }
> -- 
> 2.39.0
> 
>