Re: [PATCH next] smb: client: Fix use after free in send_done()

[Stefan Metzmacher <metze@samba.org>]

Hi Dan,

> The mempool_free() function frees "request".  Don't free the request
> until after smbd_disconnect_rdma_connection() to avoid a use after free
> bug.
> 
> Fixes: 5e65668c75c0 ("smb: client: let send_done() cleanup before calling smbd_disconnect_rdma_connection()")
> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> ---
>   fs/smb/client/smbdirect.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/smb/client/smbdirect.c b/fs/smb/client/smbdirect.c
> index 58321e483a1a..162f8d1c548a 100644
> --- a/fs/smb/client/smbdirect.c
> +++ b/fs/smb/client/smbdirect.c
> @@ -286,8 +286,8 @@ static void send_done(struct ib_cq *cq, struct ib_wc *wc)
>   	if (wc->status != IB_WC_SUCCESS || wc->opcode != IB_WC_SEND) {
>   		log_rdma_send(ERR, "wc->status=%d wc->opcode=%d\n",
>   			wc->status, wc->opcode);
> -		mempool_free(request, request->info->request_mempool);
>   		smbd_disconnect_rdma_connection(request->info);
> +		mempool_free(request, request->info->request_mempool);

The correct fix is to use 'info' instead of 'request->info'
other than that the order needs to stay that way.

I already asked Steve to squash such a change into the
original commit (which is not yet upstream).

See:
https://lore.kernel.org/linux-cifs/cover.1754308712.git.metze@samba.org/T/#m98a8607d7b83a11fd78547306836a872a2a27192

What was the test that triggered the problem?
Or did you only noticed it by looking at the code?

Thanks!
metze