Re: [PATCH][next] powerpc/vas: Fix potential NULL pointer dereference

[Tyrel Datwyler <tyreld@linux.ibm.com>]

On 10/14/21 10:03 PM, Gustavo A. R. Silva wrote:
> (!ptr && !ptr->foo) strikes again. :)
> 
> The expression (!ptr && !ptr->foo) is bogus and in case ptr is NULL,
> it leads to a NULL pointer dereference: ptr->foo.
> 
> Fix this by converting && to ||
> 
> This issue was detected with the help of Coccinelle, and audited and
> fixed manually.
> 
> Fixes: 1a0d0d5ed5e3 ("powerpc/vas: Add platform specific user window operations")
> Cc: stable@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Looking at the usage pattern it is obvious that if we determine !ptr attempting
to also confirm !ptr->ops is going to blow up.

LGTM.

Reviewed-by: Tyrel Datwyler <tyreld@linux.ibm.com>

> ---
>  arch/powerpc/platforms/book3s/vas-api.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c
> index 30172e52e16b..4d82c92ddd52 100644
> --- a/arch/powerpc/platforms/book3s/vas-api.c
> +++ b/arch/powerpc/platforms/book3s/vas-api.c
> @@ -303,7 +303,7 @@ static int coproc_ioc_tx_win_open(struct file *fp, unsigned long arg)
>  		return -EINVAL;
>  	}
> 
> -	if (!cp_inst->coproc->vops && !cp_inst->coproc->vops->open_win) {
> +	if (!cp_inst->coproc->vops || !cp_inst->coproc->vops->open_win) {
>  		pr_err("VAS API is not registered\n");
>  		return -EACCES;
>  	}
> @@ -373,7 +373,7 @@ static int coproc_mmap(struct file *fp, struct vm_area_struct *vma)
>  		return -EINVAL;
>  	}
> 
> -	if (!cp_inst->coproc->vops && !cp_inst->coproc->vops->paste_addr) {
> +	if (!cp_inst->coproc->vops || !cp_inst->coproc->vops->paste_addr) {
>  		pr_err("%s(): VAS API is not registered\n", __func__);
>  		return -EACCES;
>  	}
>