linux-kernel - Re: [PATCH v2] ksmbd: fix possible memory leak in smb2

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Date:   Tue, 7 Feb 2023 08:44:31 +0900
From:   Namjae Jeon <linkinjeon@...nel.org>
To:     Hangyu Hua <hbh25y@...il.com>
Cc:     sfrench@...ba.org, senozhatsky@...omium.org, tom@...pey.com,
        lsahlber@...hat.com, hyc.lee@...il.com, linux-cifs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ksmbd: fix possible memory leak in smb2_lock()

2023-02-06 11:36 GMT+09:00, Hangyu Hua <hbh25y@...il.com>:
> argv needs to be free when setup_async_work fails or when the current
> process is woken up.
>
> Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
> Signed-off-by: Hangyu Hua <hbh25y@...il.com>
> ---
>
> v2: avoid NULL pointer dereference in set_close_state_blocked_works()
>
>  fs/ksmbd/smb2pdu.c   | 5 +++++
>  fs/ksmbd/vfs_cache.c | 2 ++
>  2 files changed, 7 insertions(+)
>
> diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
> index d681f91947d9..177a24704021 100644
> --- a/fs/ksmbd/smb2pdu.c
> +++ b/fs/ksmbd/smb2pdu.c
> @@ -7050,6 +7050,7 @@ int smb2_lock(struct ksmbd_work *work)
>  						      smb2_remove_blocked_lock,
>  						      argv);
>  				if (rc) {
> +					kfree(argv);
>  					err = -ENOMEM;
>  					goto out;
>  				}
> @@ -7072,6 +7073,8 @@ int smb2_lock(struct ksmbd_work *work)
>  						spin_lock(&fp->f_lock);
>  						list_del(&work->fp_entry);
>  						spin_unlock(&fp->f_lock);
> +						kfree(argv);
> +						work->cancel_fn = NULL;
>  						rsp->hdr.Status =
>  							STATUS_CANCELLED;
>  						kfree(smb_lock);
> @@ -7096,6 +7099,8 @@ int smb2_lock(struct ksmbd_work *work)
>  				spin_lock(&fp->f_lock);
>  				list_del(&work->fp_entry);
>  				spin_unlock(&fp->f_lock);
> +				kfree(argv);
> +				work->cancel_fn = NULL;
This doesn't seem so simple... You have to consider the racy issue
between this change and smb2_cancel(). Also, how are you testing this
patch?

>  				goto retry;
>  			} else if (!rc) {
>  				spin_lock(&work->conn->llist_lock);
> diff --git a/fs/ksmbd/vfs_cache.c b/fs/ksmbd/vfs_cache.c
> index da9163b00350..eb95c16393b7 100644
> --- a/fs/ksmbd/vfs_cache.c
> +++ b/fs/ksmbd/vfs_cache.c
> @@ -372,6 +372,8 @@ static void set_close_state_blocked_works(struct
> ksmbd_file *fp)
>  		list_del(&cancel_work->fp_entry);
>  		cancel_work->state = KSMBD_WORK_CLOSED;
>  		cancel_work->cancel_fn(cancel_work->cancel_argv);
> +		kfree(cancel_work->cancel_argv);
> +		cancel_work->cancel_fn = NULL;
>  	}
>  	spin_unlock(&fp->f_lock);
>  }
> --
> 2.34.1
>
>