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Re: [PATCH] bisect: avoid NULL pointer dereference




Hi René,

On Mon, 8 Jan 2018, René Scharfe wrote:

> 7c117184d7 (bisect: fix off-by-one error in `best_bisection_sorted()`)
> fixed an off-by-one error, plugged a memory leak and removed a NULL
> check.  However, the pointer p *is* actually NULL if an empty list is
> passed to the function.  Let's add the check back for safety.  Bisecting
> nothing doesn't make too much sense, but that's no excuse for crashing.
> 
> Found with GCC's -Wnull-dereference.
> 
> Signed-off-by: Rene Scharfe <l.s.r@xxxxxx>
> ---
>  bisect.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/bisect.c b/bisect.c
> index 0fca17c02b..2f3008b078 100644
> --- a/bisect.c
> +++ b/bisect.c
> @@ -229,8 +229,10 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n
>  		if (i < cnt - 1)
>  			p = p->next;
>  	}
> -	free_commit_list(p->next);
> -	p->next = NULL;
> +	if (p) {
> +		free_commit_list(p->next);
> +		p->next = NULL;
> +	}
>  	strbuf_release(&buf);
>  	free(array);
>  	return list;

Isn't this identical to
https://public-inbox.org/git/20180103184852.27271-1-avarab@xxxxxxxxx/ ?

Ciao,
Dscho