[PATCH 4.14 34/37] video: hgafb: fix potential NULL pointer dereference

Greg Kroah-Hartman
2021-05-24T15:43:46Z

From: Igor Matheus Andrade Torrente <igormtorrente@gmail.com>

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.

Cc: Ferenc Bakonyi <fero@drama.obuda.kando.hu>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Igor Matheus Andrade Torrente <igormtorrente@gmail.com>
Link: https://lore.kernel.org/r/20210503115736.2104747-40-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/video/fbdev/hgafb.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)

--- a/drivers/video/fbdev/hgafb.c
+++ 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;
error:
if (release_io_ports)
release_region(0x3b0, 12);
if (release_io_port)
release_region(0x3bf, 1);
- return 0;
+
+ iounmap(hga_vram);
+
+ pr_err("hgafb: HGA card not detected.\n");
+
+ return -EINVAL;
}

/**
@@ -548,13 +555,11 @@ static struct fb_ops hgafb_ops = {
static int hgafb_probe(struct platform_device *pdev)
{
struct fb_info *info;
+ int ret;

- if (! hga_card_detect()) {
- printk(KERN_INFO "hgafb: HGA card not detected.\n");
- if (hga_vram)
- iounmap(hga_vram);
- return -EINVAL;
- }
+ 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);