linux-kernel - Re: [PATCH 9/9] x86/microcode/amd: Add __list_del_entry_valid() in front of __list_del() in free

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Message-ID: <YTCNdmeyq55UBPXK@zn.tnic>
Date:   Thu, 2 Sep 2021 10:38:14 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     jiasheng <jiasheng@...as.ac.cn>
Cc:     x86@...nel.org, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 9/9] x86/microcode/amd: Add __list_del_entry_valid() in
 front of __list_del() in free_cache()

Hello,

On Thu, Sep 02, 2021 at 01:45:22AM +0000, jiasheng wrote:
> We have found that in the complied files __list_del()
> appear more than 100 times, and under at least 90% circumstances
> that __list_del_entry_valid() and __list_del() appear in pairs.
> For example, they appear together in the __list_del_entry()
> of the header file, 'include/linux/list.h'.
> But we have found that in the free_cache(), there is only
> __list_del() instead of the pair.
> Therefore, we consider that the __list_del_entry_valid()
> might be forgotten.

if this is how you're going to "analyze" whether something is amiss
in the code - by looking at how some other code does something, i.e.,
patterns - and not involve grey matter and actually *think* what you're
doing before doing it and what those functions do, your patches will
simply get ingored.

> Signed-off-by: jiasheng <jiasheng@...as.ac.cn>

When you sign off on a patch, please give your full name.

> ---
>  arch/x86/kernel/cpu/microcode/amd.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
> index 3d4a483..1987ee1 100644
> --- a/arch/x86/kernel/cpu/microcode/amd.c
> +++ b/arch/x86/kernel/cpu/microcode/amd.c
> @@ -626,6 +626,8 @@ static void free_cache(void)
>  	struct ucode_patch *p, *tmp;
>  
>  	list_for_each_entry_safe(p, tmp, &microcode_cache, plist) {
> +		if (!__list_del_entry_valid(p->plist))
> +			continue;
>  		__list_del(p->plist.prev, p->plist.next);
>  		kfree(p->data);
>  		kfree(p);
> -- 

Also, always CC lkml when submitting patches. CCed now.

Ok, it looks like you're a newbie to this - I'd suggest you read all of
this here:

https://www.kernel.org/doc/html/latest/process/index.html

to get acquainted with how this work is usually done and then try to fix
real bugs first.

HTH.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette