linux-kernel - Re: [PATCH v9 02/27] kallsyms: avoid hardcoding buffer size

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Message-ID: <202208171236.9CA3B9D579@keescook>
Date:   Wed, 17 Aug 2022 12:37:40 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Miguel Ojeda <ojeda@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, patches@...ts.linux.dev,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>
Subject: Re: [PATCH v9 02/27] kallsyms: avoid hardcoding buffer size

On Fri, Aug 05, 2022 at 05:41:47PM +0200, Miguel Ojeda wrote:
> From: Boqun Feng <boqun.feng@...il.com>
> 
> This introduces `KSYM_NAME_LEN_BUFFER` in place of the previously
> hardcoded size of the input buffer.
> 
> It will also make it easier to update the size in a single place
> in a later patch.
> 
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> Co-developed-by: Miguel Ojeda <ojeda@...nel.org>
> Signed-off-by: Miguel Ojeda <ojeda@...nel.org>

Reviewed-by: Kees Cook <keescook@...omium.org>

Does someone want to commit to taking these "prereq" patches? These
clean-ups are nice even without adding Rust.

-Kees

> ---
>  scripts/kallsyms.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
> index 52f5488c61bc..f3c5a2623f71 100644
> --- a/scripts/kallsyms.c
> +++ b/scripts/kallsyms.c
> @@ -27,8 +27,14 @@
>  
>  #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
>  
> +#define _stringify_1(x)	#x
> +#define _stringify(x)	_stringify_1(x)
> +
>  #define KSYM_NAME_LEN		128
>  
> +/* A substantially bigger size than the current maximum. */
> +#define KSYM_NAME_LEN_BUFFER	499
> +
>  struct sym_entry {
>  	unsigned long long addr;
>  	unsigned int len;
> @@ -198,13 +204,13 @@ static void check_symbol_range(const char *sym, unsigned long long addr,
>  
>  static struct sym_entry *read_symbol(FILE *in)
>  {
> -	char name[500], type;
> +	char name[KSYM_NAME_LEN_BUFFER+1], type;
>  	unsigned long long addr;
>  	unsigned int len;
>  	struct sym_entry *sym;
>  	int rc;
>  
> -	rc = fscanf(in, "%llx %c %499s\n", &addr, &type, name);
> +	rc = fscanf(in, "%llx %c %" _stringify(KSYM_NAME_LEN_BUFFER) "s\n", &addr, &type, name);
>  	if (rc != 3) {
>  		if (rc != EOF && fgets(name, sizeof(name), in) == NULL)
>  			fprintf(stderr, "Read error or end of file.\n");
> -- 
> 2.37.1
> 

-- 
Kees Cook