linux-kernel - Re: [PATCH] x86/e820: fix the function type for e820__mapped

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Message-ID: <95513107-5aa4-5e42-467f-f9a415eb9f3f@infradead.org>
Date:   Fri, 13 Nov 2020 10:34:59 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc:     Kees Cook <keescook@...omium.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Sedat Dilek <sedat.dilek@...il.com>
Subject: Re: [PATCH] x86/e820: fix the function type for e820__mapped_all

On 11/13/20 10:26 AM, Sami Tolvanen wrote:
> e820__mapped_all is passed as a callback to is_mmconf_reserved, which
> expects a function of type:
> 
>   typedef bool (*check_reserved_t)(u64 start, u64 end, unsigned type);
> 
> This trips indirect call checking with Clang's Control-Flow Integrity
> (CFI). Change the last argument from enum e820_type to unsigned to fix
> the type mismatch.

Hi,

Kernel style is no raw unsigned -- use unsigned int or unsigned long, please.

checkpatch should or could have found that issue.

> Reported-by: Sedat Dilek <sedat.dilek@...il.com>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> ---
>  arch/x86/include/asm/e820/api.h | 2 +-
>  arch/x86/kernel/e820.c          | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/e820/api.h b/arch/x86/include/asm/e820/api.h
> index e8f58ddd06d9..e872a796619d 100644
> --- a/arch/x86/include/asm/e820/api.h
> +++ b/arch/x86/include/asm/e820/api.h
> @@ -12,7 +12,7 @@ extern unsigned long pci_mem_start;
>  
>  extern bool e820__mapped_raw_any(u64 start, u64 end, enum e820_type type);
>  extern bool e820__mapped_any(u64 start, u64 end, enum e820_type type);
> -extern bool e820__mapped_all(u64 start, u64 end, enum e820_type type);
> +extern bool e820__mapped_all(u64 start, u64 end, unsigned type);
>  
>  extern void e820__range_add   (u64 start, u64 size, enum e820_type type);
>  extern u64  e820__range_update(u64 start, u64 size, enum e820_type old_type, enum e820_type new_type);
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index 22aad412f965..9f6a4e9bca4c 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -145,7 +145,7 @@ static struct e820_entry *__e820__mapped_all(u64 start, u64 end,
>  /*
>   * This function checks if the entire range <start,end> is mapped with type.
>   */
> -bool __init e820__mapped_all(u64 start, u64 end, enum e820_type type)
> +bool __init e820__mapped_all(u64 start, u64 end, unsigned type)
>  {
>  	return __e820__mapped_all(start, end, type);
>  }
> 
> base-commit: 585e5b17b92dead8a3aca4e3c9876fbca5f7e0ba
> 


-- 
~Randy