[PATCH v4 3/5] hw/nvme: fix out-of-bounds reads

[Klaus Jensen <its@irrelevant.dk>]

From: Klaus Jensen <k.jensen@samsung.com>

Peter noticed that mmio access may read into the NvmeParams member in
the NvmeCtrl struct.

Fix the bounds check.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/nvme/ctrl.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
index 8c305315f41c..0449cc4dee9b 100644
--- a/hw/nvme/ctrl.c
+++ b/hw/nvme/ctrl.c
@@ -5968,23 +5968,26 @@ static uint64_t nvme_mmio_read(void *opaque, hwaddr addr, unsigned size)
         /* should RAZ, fall through for now */
     }
 
-    if (addr < sizeof(n->bar)) {
-        /*
-         * When PMRWBM bit 1 is set then read from
-         * from PMRSTS should ensure prior writes
-         * made it to persistent media
-         */
-        if (addr == NVME_REG_PMRSTS &&
-            (NVME_PMRCAP_PMRWBM(n->bar.pmrcap) & 0x02)) {
-            memory_region_msync(&n->pmr.dev->mr, 0, n->pmr.dev->size);
-        }
-        memcpy(&val, ptr + addr, size);
-    } else {
+    if (addr > sizeof(n->bar) - size) {
         NVME_GUEST_ERR(pci_nvme_ub_mmiord_invalid_ofs,
                        "MMIO read beyond last register,"
                        " offset=0x%"PRIx64", returning 0", addr);
+
+        return 0;
     }
 
+    /*
+     * When PMRWBM bit 1 is set then read from
+     * from PMRSTS should ensure prior writes
+     * made it to persistent media
+     */
+    if (addr == NVME_REG_PMRSTS &&
+        (NVME_PMRCAP_PMRWBM(n->bar.pmrcap) & 0x02)) {
+        memory_region_msync(&n->pmr.dev->mr, 0, n->pmr.dev->size);
+    }
+
+    memcpy(&val, ptr + addr, size);
+
     return val;
 }
 
-- 
2.32.0