[PATCH 1/1] video, sm501: Fix buffer errors in OF binding code

[David Laight <david.laight.linux@gmail.com>]

The code that gets the frame buffer mode from OF has 'use after free',
'buffer overrun' and memory leaks.

info->edid_data isn't free if the probe functions fail or if
pd->def_mode is set.

If both the CRT and PANEL are enabled info->edid_data is used after
being freed and is freed twice.

The string returned by of_get_property(np, "mode", &len) is just
written over either the static "640x480-16@60" or the module parameter
string without any regard for the length (which is most likely longer).

Use kstrump() for the OF mode and free everything before freeing 'info.

Fixes: 4295f9bf74a88 ("video, sm501: add OF binding to support SM501")
Signed-off-by: David Laight <david.laight.linux@gmail.com>
---
 drivers/video/fbdev/sm501fb.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/video/fbdev/sm501fb.c b/drivers/video/fbdev/sm501fb.c
index fee4b9f84592..ea5375ed4ea6 100644
--- a/drivers/video/fbdev/sm501fb.c
+++ b/drivers/video/fbdev/sm501fb.c
@@ -96,6 +96,7 @@ struct sm501fb_info {
 	void __iomem		*fbmem;		/* remapped framebuffer */
 	size_t			 fbmem_len;	/* length of remapped region */
 	u8 *edid_data;
+	char *fb_mode;
 };
 
 /* per-framebuffer private data */
@@ -1793,12 +1794,11 @@ static int sm501fb_init_fb(struct fb_info *fb, enum sm501_controller head,
 			fb->var.yres_virtual = fb->var.yres;
 		} else {
 			if (info->edid_data) {
-				ret = fb_find_mode(&fb->var, fb, fb_mode,
+				ret = fb_find_mode(&fb->var, fb,
+					info->fb_mode ?: fb_mode,
 					fb->monspecs.modedb,
 					fb->monspecs.modedb_len,
 					&sm501_default_mode, default_bpp);
-				/* edid_data is no longer needed, free it */
-				kfree(info->edid_data);
 			} else {
 				ret = fb_find_mode(&fb->var, fb,
 					   NULL, NULL, 0, NULL, 8);
@@ -1974,7 +1974,7 @@ static int sm501fb_probe(struct platform_device *pdev)
 			/* Get EDID */
 			cp = of_get_property(np, "mode", &len);
 			if (cp)
-				strcpy(fb_mode, cp);
+				info->fb_mode = kstrdup(cp, GFP_KERNEL);
 			prop = of_get_property(np, "edid", &len);
 			if (prop && len == EDID_LENGTH) {
 				info->edid_data = kmemdup(prop, EDID_LENGTH,
@@ -2031,6 +2031,12 @@ static int sm501fb_probe(struct platform_device *pdev)
 		goto err_started_crt;
 	}
 
+	/* These aren't needed any more */
+	kfree(info->edid_data);
+	kfree(info->fb_mode);
+	info->edid_data = NULL;
+	info->fb_mode = NULL;
+
 	/* we registered, return ok */
 	return 0;
 
@@ -2048,6 +2054,8 @@ static int sm501fb_probe(struct platform_device *pdev)
 	framebuffer_release(info->fb[HEAD_CRT]);
 
 err_alloc:
+	kfree(info->edid_data);
+	kfree(info->fb_mode);
 	kfree(info);
 
 	return ret;
-- 
2.39.5