linux-kernel - Re: [PATCH 2/2] 9p: client_create: init fcall

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Date:   Thu, 29 Sep 2022 08:57:31 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Dominique Martinet <asmadeus@...ewreck.org>
Cc:     v9fs-developer@...ts.sourceforge.net, linux_oss@...debyte.com,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH 2/2] 9p: client_create: init fcall_cache earlier

On Thu, Sep 29, 2022 at 06:44:17AM +0900, Dominique Martinet wrote:
> fcall cache was init'd last for some reason, but we actually allocate
> some requests for the version check before that.
> Moving the cache creation towards the start also makes p9_client_destroy's
> order match the allocation order, which might be easier to think about
> 
> Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
> ---
>  net/9p/client.c | 20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)

Please submit it properly. It is unclear to which series you are
referring.

> 
> diff --git a/net/9p/client.c b/net/9p/client.c
> index 40b59431a566..1ea326e6e271 100644
> --- a/net/9p/client.c
> +++ b/net/9p/client.c
> @@ -977,6 +977,17 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
>  	if (err < 0)
>  		goto out;
>  
> +	/* P9_HDRSZ + 4 is the smallest packet header we can have that is
> +	 * followed by data accessed from userspace by read
> +	 * Note we do not check for failure here because the cache is
> +	 * optional; warning will be issued on dmesg for failure.
> +	 */
> +	clnt->fcall_cache =
> +		kmem_cache_create_usercopy("9p-fcall-cache", clnt->msize,
> +					   0, 0, P9_HDRSZ + 4,
> +					   clnt->msize - (P9_HDRSZ + 4),
> +					   NULL);
> +

clnt->msize can be changed after call to ->create() if it is larger than clnt->trans_mod->maxsize).

>  	if (!clnt->trans_mod)
>  		clnt->trans_mod = v9fs_get_default_trans();
>  
> @@ -1016,15 +1027,6 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
>  	if (err)
>  		goto out;
>  
> -	/* P9_HDRSZ + 4 is the smallest packet header we can have that is
> -	 * followed by data accessed from userspace by read
> -	 */
> -	clnt->fcall_cache =
> -		kmem_cache_create_usercopy("9p-fcall-cache", clnt->msize,
> -					   0, 0, P9_HDRSZ + 4,
> -					   clnt->msize - (P9_HDRSZ + 4),
> -					   NULL);
> -
>  	return clnt;
>  
>  out:
> -- 
> 2.35.1
>