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Message-ID: <0ce67c60-7b55-6f29-2f97-9b17c1e175c0@gmail.com>
Date: Wed, 2 Nov 2022 09:37:49 -0700
From: James Smart <jsmart2021@...il.com>
To: Zheng Wang <zyytlz.wz@....com>, james.smart@...adcom.com
Cc: dick.kennedy@...adcom.com, jejb@...ux.ibm.com,
martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
hackerzheng666@...il.com, alex000young@...il.com,
security@...nel.org, linux-kernel@...r.kernel.org,
James Smart <jsmart2021@...il.com>
Subject: Re: [PATCH] scsi: lpfc: fix double free bug in
lpfc_bsg_write_ebuf_set
On 10/27/2022 10:07 PM, Zheng Wang wrote:
> When error occurs, it frees dmabuf in both lpfc_bsg_write_ebuf_set
> and lpfc_bsg_issue_mbox.
>
> Fix it by removing free code in lpfc_bsg_write_ebuf_set.
>
> Reported-by: Zheng Wang <hackerzheng666@...il.com>
> Reported-by: Zhuorao Yang <alex000young@...il.com>
>
> Fixes: 7ad20aa9d39a ("[SCSI] lpfc 8.3.24: Extend BSG infrastructure and add link diagnostics")
>
> Signed-off-by: Zheng Wang <zyytlz.wz@....com>
> ---
> drivers/scsi/lpfc/lpfc_bsg.c | 17 +++--------------
> 1 file changed, 3 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/scsi/lpfc/lpfc_bsg.c b/drivers/scsi/lpfc/lpfc_bsg.c
> index ac0c7ccf2eae..7362d9c1a50b 100644
> --- a/drivers/scsi/lpfc/lpfc_bsg.c
> +++ b/drivers/scsi/lpfc/lpfc_bsg.c
> @@ -4439,15 +4439,13 @@ lpfc_bsg_write_ebuf_set(struct lpfc_hba *phba, struct bsg_job *job,
>
> dd_data = kmalloc(sizeof(struct bsg_job_data), GFP_KERNEL);
> if (!dd_data) {
> - rc = -ENOMEM;
> - goto job_error;
> + return -ENOMEM;
> }
>
> /* mailbox command structure for base driver */
> pmboxq = mempool_alloc(phba->mbox_mem_pool, GFP_KERNEL);
> if (!pmboxq) {
> - rc = -ENOMEM;
> - goto job_error;
> + return -ENOMEM;
> }
> memset(pmboxq, 0, sizeof(LPFC_MBOXQ_t));
> pbuf = (uint8_t *)phba->mbox_ext_buf_ctx.mbx_dmabuf->virt;
Minimally, just looking at this one snippet, by returning after the
mempool_alloc() failure, we are leaking the dd_data memory just allocated.
> @@ -4480,8 +4478,7 @@ lpfc_bsg_write_ebuf_set(struct lpfc_hba *phba, struct bsg_job *job,
> lpfc_printf_log(phba, KERN_ERR, LOG_LIBDFC,
> "2970 Failed to issue SLI_CONFIG ext-buffer "
> "mailbox command, rc:x%x\n", rc);
> - rc = -EPIPE;
> - goto job_error;
> + return -EPIPE;
and this leaks both the dd_data and pmboxq memory.
> }
>
> /* wait for additional external buffers */
> @@ -4489,14 +4486,6 @@ lpfc_bsg_write_ebuf_set(struct lpfc_hba *phba, struct bsg_job *job,
> bsg_job_done(job, bsg_reply->result,
> bsg_reply->reply_payload_rcv_len);
> return SLI_CONFIG_HANDLED;
> -
> -job_error:
> - if (pmboxq)
> - mempool_free(pmboxq, phba->mbox_mem_pool);
> - lpfc_bsg_dma_page_free(phba, dmabuf);
> - kfree(dd_data);
> -
> - return rc;
> }
>
> /**
all of these errors should cause:
lpfc_bsg_write_ebuf_set() to return -Exxx
causing lpfc_bsg_handle_sli_cfg_ebuf() to return -Exxx
causing lpfc_bsg_handle_sli_cfg_ext() to return -Exxx
which causes lpfc_bsg_issue_mbox() to jump to job_done
I understand the argument is that issue_mbox deletes them, but....
job_done:
checks/frees pmboxq is allocated after the jump so it will be NULL
frees dmabuf - which was allocated prior to the jump; is freed
in freedlpfc_bsg_handle_sli_cfg_ebuf() but only in a block
that returns SLI_CONFIG_HANDLED, which is not the block that
invokes lpfc_bsg_write_ebuf_set. So it's valid to delete.
Note: there's a special case for SLI_CONFIG_HANDLED which skips
over these deletes so it's ok.
frees dd_data - which is allocated after the jump so it too will
be NULL
So - the code is fine. The SLI_CONFIG_HANDLED is a little weird, but
the logic is fine. If the patch were added it would leak memory.
I take it this was identified by some tool ?
-- james
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