staging: xgifb: ReadVBIOSTablData(): check the BIOS size

Check the BIOS size to avoid out of bounds array access. Disable LVDS
in case errors are detected.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 21 insertions, 7 deletions

diff --git a/drivers/staging/xgifb/vb_init.c b/drivers/staging/xgifb/vb_init.c
index b4383948d72a..96e2334af2a1 100644
--- a/drivers/staging/xgifb/vb_init.c
+++ b/drivers/staging/xgifb/vb_init.c
@@ -1093,13 +1093,12 @@ static void XGINew_SetDRAMSize_340(struct xgi_hw_device_info *HwDeviceExtension,
         xgifb_reg_set(pVBInfo->P3c4, 0x21, (unsigned short) (data | 0x20));
 }
 
-static u8 *xgifb_copy_rom(struct pci_dev *dev)
+static u8 *xgifb_copy_rom(struct pci_dev *dev, size_t *rom_size)
 {
         void __iomem *rom_address;
         u8 *rom_copy;
-        size_t rom_size;
 
-        rom_address = pci_map_rom(dev, &rom_size);
+        rom_address = pci_map_rom(dev, rom_size);
         if (rom_address == NULL)
                 return NULL;
 
@@ -1107,8 +1106,8 @@ static u8 *xgifb_copy_rom(struct pci_dev *dev)
         if (rom_copy == NULL)
                 goto done;
 
-        rom_size = min_t(size_t, rom_size, XGIFB_ROM_SIZE);
-        memcpy_fromio(rom_copy, rom_address, rom_size);
+        *rom_size = min_t(size_t, *rom_size, XGIFB_ROM_SIZE);
+        memcpy_fromio(rom_copy, rom_address, *rom_size);
 
 done:
         pci_unmap_rom(dev, rom_address);
@@ -1123,27 +1122,37 @@ static void ReadVBIOSTablData(struct pci_dev *pdev,
         unsigned long i;
         unsigned char j, k;
         struct XGI21_LVDSCapStruct *lvds;
+        size_t vbios_size;
 
         if (xgifb_info->chip != XG21)
                 return;
         pVBInfo->IF_DEF_LVDS = 0;
-        vbios = xgifb_copy_rom(pdev);
+        vbios = xgifb_copy_rom(pdev, &vbios_size);
         if (vbios == NULL) {
                 dev_err(&pdev->dev, "video BIOS not available\n");
                 return;
         }
+        if (vbios_size <= 0x65)
+                goto error;
         if (!(vbios[0x65] & 0x1)) {
                 vfree(vbios);
                 return;
         }
-        pVBInfo->IF_DEF_LVDS = 1;
+        if (vbios_size <= 0x317)
+                goto error;
         i = vbios[0x316] | (vbios[0x317] << 8);
+        if (vbios_size <= i - 1)
+                goto error;
         j = vbios[i - 1];
+        if (j == 0)
+                goto error;
         if (j == 0xff)
                 j = 1;
         k = 0;
         lvds = &pVBInfo->XG21_LVDSCapList[0];
         do {
+                if (vbios_size <= i + 24)
+                        goto error;
                 lvds->LVDS_Capability   = vbios[i]      | (vbios[i + 1] << 8);
                 lvds->LVDSHT            = vbios[i + 2]  | (vbios[i + 3] << 8);
                 lvds->LVDSVT            = vbios[i + 4]  | (vbios[i + 5] << 8);
@@ -1166,6 +1175,11 @@ static void ReadVBIOSTablData(struct pci_dev *pdev,
                 lvds++;
         } while (j > 0 && k < ARRAY_SIZE(XGI21_LCDCapList));
         vfree(vbios);
+        pVBInfo->IF_DEF_LVDS = 1;
+        return;
+error:
+        dev_err(&pdev->dev, "video BIOS corrupted\n");
+        vfree(vbios);
 }
 
 static void XGINew_ChkSenseStatus(struct xgi_hw_device_info *HwDeviceExtension,