James Smart <jsmart2021@xxxxxxxxx> 于2022年11月3日周四 00:37写道：
> Minimally, just looking at this one snippet, by returning after the
> mempool_alloc() failure, we are leaking the dd_data memory just allocated.
>
Yes, this is a bad patch.
> > @@ -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.
So Here it is.
>
> 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
>
Hi James! Really apprecaite for your reply. I was not sure if it it a
really issue. Sorry for the bad patch.
> 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
I understood your point. Here is a call chain :
lpfc_bsg_issue_mbox->lpfc_bsg_handle_sli_cfg_ext->lpfc_bsg_handle_sli_cfg_ebuf->lpfc_bsg_write_ebuf_set->lpfc_bsg_dma_page_free->kfree(dmabuf)
It leads to another kfree in lpfc_bsg_mbox_cmd :
job_done:
/* common exit for error or job completed inline */
if (pmboxq)
mempool_free(pmboxq, phba->mbox_mem_pool);
[7] lpfc_bsg_dma_page_free(phba, dmabuf);
kfree(dd_data);
So the key point is whether phba->mbox_ext_buf_ctx.mboxType can be
mbox_wr. If not, just as you illustrated, all is fine.
It will get into SLI_CONFIG_HANDLED path and handle dmabuf as expected.
But if not, it will have a chance to trigger a double-free bug. I
found phda is assigned in lpfc_bsg_mbox_cmd. But I am still not sure
about its value.
Appreciate if you can help me to understand more about the key condition :)
> 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 ?
>
Yes, I found it using Codeql. I didn't have a poc to verify.
Best Regards,
Zheng Wang
