netdev - Re: [patch net-next] smc: some potential use after free bugs

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Date:   Thu, 26 Jan 2017 12:23:02 +0100
From:   Ursula Braun <ubraun@...ux.vnet.ibm.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [patch net-next] smc: some potential use after free bugs


On 01/26/2017 10:05 AM, Dan Carpenter wrote:
> Say we got really unlucky and these failed on the last iteration, then
> it could lead to a use after free bug.
thanks for reporting this! I had already a similar patch prepared, but not
yet submitted. It contains all your added lines plus these additional
pre-initializations at definition time:

@@ -509,7 +509,7 @@ int smc_sndbuf_create(struct smc_sock *smc)
        struct smc_connection *conn = &smc->conn;
        struct smc_link_group *lgr = conn->lgr;
        int tmp_bufsize, tmp_bufsize_short;
-   struct smc_buf_desc *sndbuf_desc;
+ struct smc_buf_desc *sndbuf_desc = NULL;
        int rc;
 
        /* use socket send buffer size (w/o overhead) as start value */

@@ -573,7 +575,7 @@ int smc_rmb_create(struct smc_sock *smc)
        struct smc_connection *conn = &smc->conn;
        struct smc_link_group *lgr = conn->lgr;
        int tmp_bufsize, tmp_bufsize_short;
-   struct smc_buf_desc *rmb_desc;
+ struct smc_buf_desc *rmb_desc = NULL;
        int rc;
 
        /* use socket recv buffer size (w/o overhead) as start value */

If you do not contradict, I will post my enhanced patch version.
> 
> Fixes: cd6851f30386 ("smc: remote memory buffers (RMBs)")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> 
> diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
> index 8b1d34378829..941279e1504e 100644
> --- a/net/smc/smc_core.c
> +++ b/net/smc/smc_core.c
> @@ -535,6 +535,7 @@ int smc_sndbuf_create(struct smc_sock *smc)
>  			/* if send buffer allocation has failed,
>  			 * try a smaller one
>  			 */
> +			sndbuf_desc = NULL;
>  			continue;
>  		}
>  		rc = smc_ib_buf_map(lgr->lnk[SMC_SINGLE_LINK].smcibdev,
> @@ -543,6 +544,7 @@ int smc_sndbuf_create(struct smc_sock *smc)
>  		if (rc) {
>  			kfree(sndbuf_desc->cpu_addr);
>  			kfree(sndbuf_desc);
> +			sndbuf_desc = NULL;
>  			continue; /* if mapping failed, try smaller one */
>  		}
>  		sndbuf_desc->used = 1;
> @@ -599,6 +601,7 @@ int smc_rmb_create(struct smc_sock *smc)
>  			/* if RMB allocation has failed,
>  			 * try a smaller one
>  			 */
> +			rmb_desc = NULL;
>  			continue;
>  		}
>  		rc = smc_ib_buf_map(lgr->lnk[SMC_SINGLE_LINK].smcibdev,
> @@ -607,6 +610,7 @@ int smc_rmb_create(struct smc_sock *smc)
>  		if (rc) {
>  			kfree(rmb_desc->cpu_addr);
>  			kfree(rmb_desc);
> +			rmb_desc = NULL;
>  			continue; /* if mapping failed, try smaller one */
>  		}
>  		rc = smc_ib_get_memory_region(lgr->lnk[SMC_SINGLE_LINK].roce_pd,
> @@ -619,6 +623,7 @@ int smc_rmb_create(struct smc_sock *smc)
>  					 DMA_FROM_DEVICE);
>  			kfree(rmb_desc->cpu_addr);
>  			kfree(rmb_desc);
> +			rmb_desc = NULL;
>  			continue;
>  		}
>  		rmb_desc->used = 1;
>