[Crash-utility] [PATCH v4 2/4] Get the absolute value of SYMNAME_HASH_INDEX

[lijiang]

> Date: Sat, 18 Sep 2021 15:59:30 +0800
> From: Tao Liu <ltao at redhat.com>
> To: crash-utility at redhat.com
> Subject: [Crash-utility] [PATCH v4 2/4] Get the absolute value of
>         SYMNAME_HASH_INDEX
> Message-ID: <20210918075932.132339-3-ltao at redhat.com>
> Content-Type: text/plain; charset="US-ASCII"
>
> SYMNAME_HASH_INDEX is used as the index of symname hash table. It will
> be out of range if SYMNAME_HASH_INDEX is negative. Let's get its absolute
> value to avoid such risk.
>
> Signed-off-by: Tao Liu <ltao at redhat.com>
> Reviewed-by: Philipp Rudo <prudo at redhat.com>
> ---
>  defs.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/defs.h b/defs.h
> index c10ebff..3129f06 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -2725,7 +2725,7 @@ struct downsized {
>
>  #define SYMNAME_HASH (512)
>  #define SYMNAME_HASH_INDEX(name) \
> - ((name[0] ^ (name[strlen(name)-1] * name[strlen(name)/2])) % SYMNAME_HASH)
> + (abs((name[0] ^ (name[strlen(name)-1] * name[strlen(name)/2])) % SYMNAME_HASH))
>

I guess this may be caused by integer overflow, the expression uses
integer calculations by default.  Does the following change work for
you?

-#define SYMNAME_HASH (512)
+#define SYMNAME_HASH (512ULL)

Thanks.
Lianbo
>  #define PATCH_KERNEL_SYMBOLS_START  ((char *)(1))
>  #define PATCH_KERNEL_SYMBOLS_STOP   ((char *)(2))
> --
> 2.29.2
>