linux-kernel - Re: [PATCH v3] ksmbd: fix possible memory leak in smb2

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Message-ID: <CAKYAXd-0oHPS4ca4j7rPTe6i4EgZqvx2ukYkJ0NqaFh2gmkK3Q@mail.gmail.com>
Date:   Tue, 14 Feb 2023 08:35:18 +0900
From:   Namjae Jeon <linkinjeon@...nel.org>
To:     Hangyu Hua <hbh25y@...il.com>
Cc:     sfrench@...ba.org, senozhatsky@...omium.org, tom@...pey.com,
        hyc.lee@...il.com, lsahlber@...hat.com, linux-cifs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] ksmbd: fix possible memory leak in smb2_lock()

2023-02-07 17:07 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()
> v3: avoid race condition between smb2_lock() and smb2_cancel()
>
>  fs/ksmbd/smb2pdu.c   | 23 ++++++++++++++---------
>  fs/ksmbd/vfs_cache.c |  2 ++
>  2 files changed, 16 insertions(+), 9 deletions(-)
>
> diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
> index d681f91947d9..f4079518eaf6 100644
> --- a/fs/ksmbd/smb2pdu.c
> +++ b/fs/ksmbd/smb2pdu.c
> @@ -6644,7 +6644,7 @@ int smb2_cancel(struct ksmbd_work *work)
>  	struct ksmbd_conn *conn = work->conn;
>  	struct smb2_hdr *hdr = smb2_get_msg(work->request_buf);
>  	struct smb2_hdr *chdr;
> -	struct ksmbd_work *cancel_work = NULL, *iter;
> +	struct ksmbd_work *iter;
>  	struct list_head *command_list;
>
>  	ksmbd_debug(SMB, "smb2 cancel called on mid %llu, async flags 0x%x\n",
> @@ -6666,7 +6666,9 @@ int smb2_cancel(struct ksmbd_work *work)
>  				    "smb2 with AsyncId %llu cancelled command = 0x%x\n",
>  				    le64_to_cpu(hdr->Id.AsyncId),
>  				    le16_to_cpu(chdr->Command));
> -			cancel_work = iter;
> +			iter->state = KSMBD_WORK_CANCELLED;
> +			if (iter->cancel_fn)
> +				iter->cancel_fn(iter->cancel_argv);
>  			break;
>  		}
>  		spin_unlock(&conn->request_lock);
> @@ -6685,18 +6687,12 @@ int smb2_cancel(struct ksmbd_work *work)
>  				    "smb2 with mid %llu cancelled command = 0x%x\n",
>  				    le64_to_cpu(hdr->MessageId),
>  				    le16_to_cpu(chdr->Command));
> -			cancel_work = iter;
> +			iter->state = KSMBD_WORK_CANCELLED;
>  			break;
>  		}
>  		spin_unlock(&conn->request_lock);
>  	}
>
> -	if (cancel_work) {
> -		cancel_work->state = KSMBD_WORK_CANCELLED;
> -		if (cancel_work->cancel_fn)
> -			cancel_work->cancel_fn(cancel_work->cancel_argv);
> -	}
> -
>  	/* For SMB2_CANCEL command itself send no response*/
>  	work->send_no_response = 1;
>  	return 0;
> @@ -7050,6 +7046,7 @@ int smb2_lock(struct ksmbd_work *work)
>  						      smb2_remove_blocked_lock,
>  						      argv);
>  				if (rc) {
> +					kfree(argv);
>  					err = -ENOMEM;
>  					goto out;
>  				}
> @@ -7061,6 +7058,10 @@ int smb2_lock(struct ksmbd_work *work)
>
>  				ksmbd_vfs_posix_lock_wait(flock);
>
> +				spin_lock(&work->conn->request_lock);
> +				list_del_init(&work->async_request_entry);
It is called again in ksmbd_conn_try_dequeue_request().
> +				spin_unlock(&work->conn->request_lock);
> +