linux-kernel - Re: [PATCH v2] modpost: abort if a module symbol is too long

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Message-ID: <87io8qbabs.fsf@rustcorp.com.au>
Date:	Sat, 08 Aug 2015 15:17:35 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] modpost: abort if a module symbol is too long

Takashi Iwai <tiwai@...e.de> writes:
> Module symbols have a limited length, but currently the build system
> allows the build finishing even if the driver code contains a too long
> symbol name, which eventually overflows the modversion_info[] item.
> The compiler may catch at compiling *.mod.c like
>   CC      xxx.mod.o
>   xxx.mod.c:18:16: warning: initializer-string for array of chars is too long
> but it's merely a warning.

Thanks, applied!

Cheers,
Rusty.

>
> This patch adds the check of the symbol length in modpost and stops
> the build properly.
>
> Currently MODULE_NAME_LEN is defined in modpost.c instead of referring
> to the definition in kernel header because including linux/module.h is
> messy and we must cover cross-compilation.
>
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> ---
> v1->v2: Fix MODULE_NAME_LEN to use Elf_Addr
>
>  scripts/mod/modpost.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 12d3db3bd46b..d583c98fde31 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -2133,6 +2133,11 @@ static void add_staging_flag(struct buffer *b, const char *name)
>  		buf_printf(b, "\nMODULE_INFO(staging, \"Y\");\n");
>  }
>  
> +/* In kernel, this size is defined in linux/module.h;
> + * here we use Elf_Addr instead of long for covering cross-compile
> + */
> +#define MODULE_NAME_LEN (64 - sizeof(Elf_Addr))
> +
>  /**
>   * Record CRCs for unresolved symbols
>   **/
> @@ -2177,6 +2182,12 @@ static int add_versions(struct buffer *b, struct module *mod)
>  				s->name, mod->name);
>  			continue;
>  		}
> +		if (strlen(s->name) >= MODULE_NAME_LEN) {
> +			merror("too long symbol \"%s\" [%s.ko]\n",
> +			       s->name, mod->name);
> +			err = 1;
> +			break;
> +		}
>  		buf_printf(b, "\t{ %#8x, __VMLINUX_SYMBOL_STR(%s) },\n",
>  			   s->crc, s->name);
>  	}
> -- 
> 2.5.0
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