Hi Pavel,
On 5/25/21 5:47 PM, Pavel Machek wrote:
Hi!
From: Igor Matheus Andrade Torrente <igormtorrente@xxxxxxxxx>
commit dc13cac4862cc68ec74348a80b6942532b7735fa upstream.
The return of ioremap if not checked, and can lead to a NULL to be
assigned to hga_vram. Potentially leading to a NULL pointer
dereference.
The fix adds code to deal with this case in the error label and
changes how the hgafb_probe handles the return of hga_card_detect.
This will break hgafb completely, right? And crash system without hga
card as a bonus.
+++ b/drivers/video/fbdev/hgafb.c
@@ -285,6 +285,8 @@ static int hga_card_detect(void)
hga_vram_len = 0x08000;
hga_vram = ioremap(0xb0000, hga_vram_len);
+ if (!hga_vram)
+ return -ENOMEM;
if (request_region(0x3b0, 12, "hgafb"))
release_io_ports = 1;
@@ -344,13 +346,18 @@ static int hga_card_detect(void)
hga_type_name = "Hercules";
break;
}
- return 1;
+ return 0;
Ok, so calling convention is now "0 means detected".
@@ -548,13 +555,11 @@ static struct fb_ops hgafb_ops = {
static int hgafb_probe(struct platform_device *pdev)
{
struct fb_info *info;
+ int ret;
...
+ ret = hga_card_detect();
+ if (!ret)
+ return ret;
printk(KERN_INFO "hgafb: %s with %ldK of memory detected.\n",
hga_type_name, hga_vram_len/1024);
If the card is detected, 0 is returned, !0 is true, and we abort
detection....
Yes, you are right! There's a patch that fixes it:
https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git/commit/?h=char-misc-linus&id=02625c965239b71869326dd0461615f27307ecb3
As far as I know, this patch should be queue up soon to all stable branches.
Greg should have more details about it.
Pavel
Signed-off-by: Pavel Machek <pavel@xxxxxxx>
diff --git a/drivers/video/fbdev/hgafb.c b/drivers/video/fbdev/hgafb.c
index c35f217db53f..d6a95ea49c64 100644
--- a/drivers/video/fbdev/hgafb.c
+++ b/drivers/video/fbdev/hgafb.c
@@ -282,7 +282,7 @@ static int hga_card_detect(void)
void __iomem *p, *q;
unsigned short p_save, q_save;
- hga_vram_len = 0x08000;
+ hga_vram_len = 0x08000;
hga_vram = ioremap(0xb0000, hga_vram_len);
if (!hga_vram)
@@ -558,7 +558,7 @@ static int hgafb_probe(struct platform_device *pdev)
int ret;
ret = hga_card_detect();
- if (!ret)
+ if (ret)
return ret;
printk(KERN_INFO "hgafb: %s with %ldK of memory detected.\n",
Thanks,
---
Igor M. A. Torrente
