Re: [PATCH v5] drm/ast: Fixed CVE for DP501

From: Thomas Zimmermann
Date: Tue Apr 27 2021 - 07:01:51 EST

Hi

Am 21.04.21 um 10:58 schrieb KuoHsiang Chou:
[Bug][DP501]
If ASPEED P2A (PCI to AHB) bridge is disabled and disallowed for
CVE_2019_6260 item3, and then the monitor's EDID is unable read through
Parade DP501.
The reason is the DP501's FW is mapped to BMC addressing space rather
than Host addressing space.
The resolution is that using "pci_iomap_range()" maps to DP501's FW that
stored on the end of FB (Frame Buffer).
In this case, FrameBuffer reserves the last 2MB used for the image of
DP501.


Your patches are missing a short changelog, so that reviewers can see what changed between versions. Anyway, I merged your patch into drm-misc-next now. Thanks for the fix.


More generally speaking, the DP501 code needs a major refactoring. It's currently bolted onto the regular VGA connector code. It should rather be a separate connector or a DRM bridge. I always wanted to work on this, but don't have a device for testing. If I'd provide patches, would you be in a position to test them?

Best regards
Thomas


Signed-off-by: KuoHsiang Chou <kuohsiang_chou@xxxxxxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
---
drivers/gpu/drm/ast/ast_dp501.c | 139 +++++++++++++++++++++++---------
drivers/gpu/drm/ast/ast_drv.h | 12 +++
drivers/gpu/drm/ast/ast_main.c | 11 ++-
3 files changed, 125 insertions(+), 37 deletions(-)

diff --git a/drivers/gpu/drm/ast/ast_dp501.c b/drivers/gpu/drm/ast/ast_dp501.c
index 88121c0e0..cd93c44f2 100644
--- a/drivers/gpu/drm/ast/ast_dp501.c
+++ b/drivers/gpu/drm/ast/ast_dp501.c
@@ -189,6 +189,9 @@ bool ast_backup_fw(struct drm_device *dev, u8 *addr, u32 size)
u32 i, data;
u32 boot_address;

+ if (ast->config_mode != ast_use_p2a)
+ return false;
+
data = ast_mindwm(ast, 0x1e6e2100) & 0x01;
if (data) {
boot_address = get_fw_base(ast);
@@ -207,6 +210,9 @@ static bool ast_launch_m68k(struct drm_device *dev)
u8 *fw_addr = NULL;
u8 jreg;

+ if (ast->config_mode != ast_use_p2a)
+ return false;
+
data = ast_mindwm(ast, 0x1e6e2100) & 0x01;
if (!data) {

@@ -271,25 +277,55 @@ u8 ast_get_dp501_max_clk(struct drm_device *dev)
struct ast_private *ast = to_ast_private(dev);
u32 boot_address, offset, data;
u8 linkcap[4], linkrate, linklanes, maxclk = 0xff;
+ u32 *plinkcap;

- boot_address = get_fw_base(ast);
-
- /* validate FW version */
- offset = 0xf000;
- data = ast_mindwm(ast, boot_address + offset);
- if ((data & 0xf0) != 0x10) /* version: 1x */
- return maxclk;
-
- /* Read Link Capability */
- offset = 0xf014;
- *(u32 *)linkcap = ast_mindwm(ast, boot_address + offset);
- if (linkcap[2] == 0) {
- linkrate = linkcap[0];
- linklanes = linkcap[1];
- data = (linkrate == 0x0a) ? (90 * linklanes) : (54 * linklanes);
- if (data > 0xff)
- data = 0xff;
- maxclk = (u8)data;
+ if (ast->config_mode == ast_use_p2a) {
+ boot_address = get_fw_base(ast);
+
+ /* validate FW version */
+ offset = AST_DP501_GBL_VERSION;
+ data = ast_mindwm(ast, boot_address + offset);
+ if ((data & AST_DP501_FW_VERSION_MASK) != AST_DP501_FW_VERSION_1) /* version: 1x */
+ return maxclk;
+
+ /* Read Link Capability */
+ offset = AST_DP501_LINKRATE;
+ plinkcap = (u32 *)linkcap;
+ *plinkcap = ast_mindwm(ast, boot_address + offset);
+ if (linkcap[2] == 0) {
+ linkrate = linkcap[0];
+ linklanes = linkcap[1];
+ data = (linkrate == 0x0a) ? (90 * linklanes) : (54 * linklanes);
+ if (data > 0xff)
+ data = 0xff;
+ maxclk = (u8)data;
+ }
+ } else {
+ if (!ast->dp501_fw_buf)
+ return AST_DP501_DEFAULT_DCLK; /* 1024x768 as default */
+
+ /* dummy read */
+ offset = 0x0000;
+ data = readl(ast->dp501_fw_buf + offset);
+
+ /* validate FW version */
+ offset = AST_DP501_GBL_VERSION;
+ data = readl(ast->dp501_fw_buf + offset);
+ if ((data & AST_DP501_FW_VERSION_MASK) != AST_DP501_FW_VERSION_1) /* version: 1x */
+ return maxclk;
+
+ /* Read Link Capability */
+ offset = AST_DP501_LINKRATE;
+ plinkcap = (u32 *)linkcap;
+ *plinkcap = readl(ast->dp501_fw_buf + offset);
+ if (linkcap[2] == 0) {
+ linkrate = linkcap[0];
+ linklanes = linkcap[1];
+ data = (linkrate == 0x0a) ? (90 * linklanes) : (54 * linklanes);
+ if (data > 0xff)
+ data = 0xff;
+ maxclk = (u8)data;
+ }
}
return maxclk;
}
@@ -298,26 +334,57 @@ bool ast_dp501_read_edid(struct drm_device *dev, u8 *ediddata)
{
struct ast_private *ast = to_ast_private(dev);
u32 i, boot_address, offset, data;
+ u32 *pEDIDidx;

- boot_address = get_fw_base(ast);
-
- /* validate FW version */
- offset = 0xf000;
- data = ast_mindwm(ast, boot_address + offset);
- if ((data & 0xf0) != 0x10)
- return false;
-
- /* validate PnP Monitor */
- offset = 0xf010;
- data = ast_mindwm(ast, boot_address + offset);
- if (!(data & 0x01))
- return false;
+ if (ast->config_mode == ast_use_p2a) {
+ boot_address = get_fw_base(ast);

- /* Read EDID */
- offset = 0xf020;
- for (i = 0; i < 128; i += 4) {
- data = ast_mindwm(ast, boot_address + offset + i);
- *(u32 *)(ediddata + i) = data;
+ /* validate FW version */
+ offset = AST_DP501_GBL_VERSION;
+ data = ast_mindwm(ast, boot_address + offset);
+ if ((data & AST_DP501_FW_VERSION_MASK) != AST_DP501_FW_VERSION_1)
+ return false;
+
+ /* validate PnP Monitor */
+ offset = AST_DP501_PNPMONITOR;
+ data = ast_mindwm(ast, boot_address + offset);
+ if (!(data & AST_DP501_PNP_CONNECTED))
+ return false;
+
+ /* Read EDID */
+ offset = AST_DP501_EDID_DATA;
+ for (i = 0; i < 128; i += 4) {
+ data = ast_mindwm(ast, boot_address + offset + i);
+ pEDIDidx = (u32 *)(ediddata + i);
+ *pEDIDidx = data;
+ }
+ } else {
+ if (!ast->dp501_fw_buf)
+ return false;
+
+ /* dummy read */
+ offset = 0x0000;
+ data = readl(ast->dp501_fw_buf + offset);
+
+ /* validate FW version */
+ offset = AST_DP501_GBL_VERSION;
+ data = readl(ast->dp501_fw_buf + offset);
+ if ((data & AST_DP501_FW_VERSION_MASK) != AST_DP501_FW_VERSION_1)
+ return false;
+
+ /* validate PnP Monitor */
+ offset = AST_DP501_PNPMONITOR;
+ data = readl(ast->dp501_fw_buf + offset);
+ if (!(data & AST_DP501_PNP_CONNECTED))
+ return false;
+
+ /* Read EDID */
+ offset = AST_DP501_EDID_DATA;
+ for (i = 0; i < 128; i += 4) {
+ data = readl(ast->dp501_fw_buf + offset + i);
+ pEDIDidx = (u32 *)(ediddata + i);
+ *pEDIDidx = data;
+ }
}

return true;
diff --git a/drivers/gpu/drm/ast/ast_drv.h b/drivers/gpu/drm/ast/ast_drv.h
index e82ab8628..911f9f414 100644
--- a/drivers/gpu/drm/ast/ast_drv.h
+++ b/drivers/gpu/drm/ast/ast_drv.h
@@ -150,6 +150,7 @@ struct ast_private {

void __iomem *regs;
void __iomem *ioregs;
+ void __iomem *dp501_fw_buf;

enum ast_chip chip;
bool vga2_clone;
@@ -325,6 +326,17 @@ int ast_mode_config_init(struct ast_private *ast);
#define AST_MM_ALIGN_SHIFT 4
#define AST_MM_ALIGN_MASK ((1 << AST_MM_ALIGN_SHIFT) - 1)

+#define AST_DP501_FW_VERSION_MASK GENMASK(7, 4)
+#define AST_DP501_FW_VERSION_1 BIT(4)
+#define AST_DP501_PNP_CONNECTED BIT(1)
+
+#define AST_DP501_DEFAULT_DCLK 65
+
+#define AST_DP501_GBL_VERSION 0xf000
+#define AST_DP501_PNPMONITOR 0xf010
+#define AST_DP501_LINKRATE 0xf014
+#define AST_DP501_EDID_DATA 0xf020
+
int ast_mm_init(struct ast_private *ast);

/* ast post */
diff --git a/drivers/gpu/drm/ast/ast_main.c b/drivers/gpu/drm/ast/ast_main.c
index 0ac3c2039..3976a2587 100644
--- a/drivers/gpu/drm/ast/ast_main.c
+++ b/drivers/gpu/drm/ast/ast_main.c
@@ -99,7 +99,7 @@ static void ast_detect_config_mode(struct drm_device *dev, u32 *scu_rev)
if (!(jregd0 & 0x80) || !(jregd1 & 0x10)) {
/* Double check it's actually working */
data = ast_read32(ast, 0xf004);
- if (data != 0xFFFFFFFF) {
+ if ((data != 0xFFFFFFFF) && (data != 0x00)) {
/* P2A works, grab silicon revision */
ast->config_mode = ast_use_p2a;

@@ -411,6 +411,7 @@ struct ast_private *ast_device_create(const struct drm_driver *drv,
return ast;
dev = &ast->base;

+ dev->pdev = pdev;
pci_set_drvdata(pdev, dev);

ast->regs = pci_iomap(pdev, 1, 0);
@@ -450,6 +451,14 @@ struct ast_private *ast_device_create(const struct
drm_driver *drv,
if (ret)
return ERR_PTR(ret);

+ /* map reserved buffer */
+ ast->dp501_fw_buf = NULL;
+ if (dev->vram_mm->vram_size < pci_resource_len(dev->pdev, 0)) {
+ ast->dp501_fw_buf = pci_iomap_range(dev->pdev, 0, dev->vram_mm->vram_size, 0);
+ if (!ast->dp501_fw_buf)
+ drm_info(dev, "failed to map reserved buffer!\n");
+ }
+
ret = ast_mode_config_init(ast);
if (ret)
return ERR_PTR(ret);
--
2.18.4

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--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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