Re: [PATCH 2/9] ftrace: Fix possible NULL dereferencing in__ftrace_hash_rec_update

[Steven Rostedt]

On Sun, 2011-11-27 at 19:04 +0100, Jiri Olsa wrote:
> We need to check the existence of the other_hash before
> we touch its count variable.
> 
> This issue is hit only when non global ftrace_ops is used.
> The global ftrace_ops is initialized with empty hashes.
> 
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
>  kernel/trace/ftrace.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index b1e8943..c6d0293 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -1372,7 +1372,8 @@ static void __ftrace_hash_rec_update(struct ftrace_ops *ops,
>  			if (filter_hash && in_hash && !in_other_hash)
>  				match = 1;
>  			else if (!filter_hash && in_hash &&
> -				 (in_other_hash || !other_hash->count))
> +				 (in_other_hash ||
> +				  !other_hash || !other_hash->count))

Thanks! I hit this bug in too many places. I need to make a helper
routine, which I think I will, that is:

	hash_has_contents(hash)

that does the check for us.

-- Steve

>  				match = 1;
>  		}
>  		if (!match)


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