linux-kernel - Re: [PATCH] dmi_scan: proper buf type in dmi

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Date:	Thu, 14 Mar 2013 00:31:53 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Artem Savkov <artem.savkov@...il.com>
Cc:	tmhikaru@...il.com, akpm@...ux-foundation.org,
	zhenzhong.duan@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmi_scan: proper buf type in dmi_present()

On Wed, 2013-03-13 at 00:17 +0400, Artem Savkov wrote:
> buf needs to be unsigned in dmi_present(), otherwise dmi_base calculation
> doesn't work properly leading to a wraparound during dmi_ioremap:
> 
> [    0.000000] ------------[ cut here ]------------
> [    0.000000] WARNING: at arch/x86/mm/ioremap.c:524 __early_ioremap+0x85/0x18a()
> [    0.000000] Modules linked in:
> [    0.000000] Pid: 0, comm: swapper Not tainted 3.9.0-rc2-next-20130312 #283
> [    0.000000] Call Trace:
> [    0.000000]  [<c1036992>] warn_slowpath_common+0x72/0xa0
> [    0.000000]  [<c19cc176>] ? __early_ioremap+0x85/0x18a
> [    0.000000]  [<c19cc176>] ? __early_ioremap+0x85/0x18a
> [    0.000000]  [<c10369e2>] warn_slowpath_null+0x22/0x30
> [    0.000000]  [<c19cc176>] __early_ioremap+0x85/0x18a
> [    0.000000]  [<c19cc1ed>] ? __early_ioremap+0xfc/0x18a
> [    0.000000]  [<c19cc412>] early_ioremap+0xd/0xf
> [    0.000000]  [<c19fbba9>] dmi_present+0xf5/0x22a
> [    0.000000]  [<c19fbd9d>] dmi_scan_machine+0xbf/0x11c
> [    0.000000]  [<c19bd781>] setup_arch+0x4db/0xca0
> [    0.000000]  [<c168105c>] ? printk+0x3d/0x3f
> [    0.000000]  [<c19ba763>] start_kernel+0x7b/0x329
> [    0.000000]  [<c19ba361>] i386_start_kernel+0x137/0x13a
> [    0.000000] ---[ end trace 4eaa2a86a8e2da22 ]---
> [    0.000000] DMI not present or invalid.
> 
> Introduced in "dmi_scan: refactor dmi_scan_machine(), {smbios,dmi}_present()"
> 
> Signed-off-by: Artem Savkov <artem.savkov@...il.com>
Acked-by: Ben Hutchings <ben@...adent.org.uk>

Wow, this is a pretty obvious fix.  Somehow this code did work for at
least two of us, so I suppose we were (un)lucky to have bit 7 clear on
all the critical bytes!

Ben.

> ---
>  drivers/firmware/dmi_scan.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
> index 3439f59..40e940d 100644
> --- a/drivers/firmware/dmi_scan.c
> +++ b/drivers/firmware/dmi_scan.c
> @@ -410,7 +410,7 @@ static void __init dmi_dump_ids(void)
>  	printk(KERN_CONT "\n");
>  }
>  
> -static int __init dmi_present(const char *buf)
> +static int __init dmi_present(const u8 *buf)
>  {
>  	int smbios_ver;
>  

-- 
Ben Hutchings
Humans are not rational beings; they are rationalising beings.

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