Messages in this thread | | | Subject | Re: [PATCH 4.4 28/31] video: hgafb: fix potential NULL pointer dereference | From | Igor Torrente <> | Date | Tue, 25 May 2021 18:06:15 -0300 |
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Hi Pavel,
On 5/25/21 5:47 PM, Pavel Machek wrote: > Hi! > >> 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. > > 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@denx.de> > > 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
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