Re: Re: Re: [PATCH v2] RDMA/srpt: fix NULL deref when sending BUSY before target_init_cmd()

[Leon Romanovsky]

On Mon, Jul 27, 2026 at 02:39:08PM +0800, kensanya wrote:
> 
> 
> At 2026-07-26 15:55:11, "Leon Romanovsky" <leon@xxxxxxxxxx> wrote:
> >On Fri, Jul 24, 2026 at 10:42:53AM +0800, kensanya wrote:
> >> At 2026-07-23 17:51:20, "Leon Romanovsky" <leon@xxxxxxxxxx> wrote:
> >> >On Thu, Jul 23, 2026 at 10:44:56AM +0800, kensanya@xxxxxxx wrote:
> >> >> From: TanZheng <tanzheng@xxxxxxxxxx>
> >> >> 
> >> >> If srpt_get_desc_tbl() fails, srpt_handle_cmd() jumps to
> >> >> target_send_busy() before target_init_cmd() has set cmd->se_tfo.
> >> >> target_send_busy() then dereferences a NULL se_tfo.
> >> >> 
> >> >> Call target_init_cmd() first with placeholder data_length and
> >> >> data_direction, parse the descriptor table next, then fill in the
> >> >> real data_length. That way target_send_busy() is safe if parsing
> >> >> fails.
> >> >> 
> >> >> target_send_busy() is only valid after a successful target_init_cmd().
> >> >> If target_init_cmd() itself fails, free the send ioctx tag locally
> >> >> with target_free_tag() instead of calling target_send_busy().
> >> >> 
> >> >> Fixes: 8b8807b9e982 ("scsi: RDMA/srpt: Fix handling of command / TMF submission failure")
> >> >> Link: https://lore.kernel.org/all/20260717025402.64054-1-kensanya@xxxxxxx/
> >> >> Suggested-by: Bart Van Assche <bvanassche@xxxxxxx>
> >> >> Signed-off-by: TanZheng <tanzheng@xxxxxxxxxx>
> >> >> ---
> >> >> v2:
> >> >> - On target_init_cmd() failure, use target_free_tag() instead of
> >> >>   target_send_busy()
> >> >> 
> >> >>  drivers/infiniband/ulp/srpt/ib_srpt.c | 36 +++++++++++++++++++--------
> >> >>  1 file changed, 26 insertions(+), 10 deletions(-)
> >> >> 
> >> >> diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.c b/drivers/infiniband/ulp/srpt/ib_srpt.c
> >> >> index f66cfd70c263..71af1fb0d380 100644
> >> >> --- a/drivers/infiniband/ulp/srpt/ib_srpt.c
> >> >> +++ b/drivers/infiniband/ulp/srpt/ib_srpt.c
> >> >> @@ -1558,8 +1558,8 @@ static void srpt_handle_cmd(struct srpt_rdma_ch *ch,
> >> >>  	struct srp_cmd *srp_cmd;
> >> >>  	struct scatterlist *sg = NULL;
> >> >>  	unsigned sg_cnt = 0;
> >> >> -	u64 data_len;
> >> >> -	enum dma_data_direction dir;
> >> >> +	u64 data_len = 0;
> >> >> +	enum dma_data_direction dir = DMA_NONE;
> >> >>  	int rc;
> >> >>  
> >> >>  	BUG_ON(!send_ioctx);
> >> >> @@ -1584,6 +1584,25 @@ static void srpt_handle_cmd(struct srpt_rdma_ch *ch,
> >> >>  		break;
> >> >>  	}
> >> >>  
> >> >> +	/*
> >> >> +	 * Call target_init_cmd() before srpt_get_desc_tbl() so that
> >> >> +	 * cmd->se_tfo is set if descriptor parsing fails and
> >> >> +	 * target_send_busy() is used. data_length is filled in after a
> >> >> +	 * successful srpt_get_desc_tbl().
> >> >> +	 *
> >> >> +	 * target_send_busy() is only valid after a successful
> >> >> +	 * target_init_cmd(). On init failure free the tag locally.
> >> >> +	 */
> >> >> +	rc = target_init_cmd(cmd, ch->sess, &send_ioctx->sense_data[0],
> >> >> +			     scsilun_to_int(&srp_cmd->lun), 0 /* data_len */,
> >> >> +			     TCM_SIMPLE_TAG, DMA_NONE, TARGET_SCF_ACK_KREF);
> >> >
> >> >1. TCM_SIMPLE_TAG -> you need to rebase to latest rdma-next.
> >> 
> >>       I will modify and resend the patch.
> >> 
> >> >2. You are hardcoding dir, while it can be overwritten in srpt_get_desc_tbl().
> >> 
> >>       In the srpt_handle_cmd() function:
> >>       &send_ioctx->cmd;
> >>       srpt_get_desc_tbl(..., send_ioctx, ...) 
> >>            ioctx->cmd.data_direction = *dir;
> >> 
> >>      Therefore, after successfully calling srpt_get_desc_tbl(), even if target_init_cmd() is
> >>      passed DMA_NONE, cmd->data_direction should already have stored the actual direction.
> >> 
> >>      Do you mean  that after calling srpt_get_desc_tbl(), displaying the overwritten content
> >>      would be better？I want to make sure I address the intent of your comment correctly.
> >
> >You need to do this correctly: target_init_cmd() must receive the
> >correct directory, as calculated by srpt_get_desc_tbl().
> >
> >Thanks
> >
> >> >
> >> >Thanks
> >> 
> >> Thanks,
> >> TanZheng
> 
> There is a contradiction between the two suggestions:
> - Bart suggests calling target_init_cmd() before calling
>    srpt_get_desc_tbl() (using a placeholder) to ensure that
>    target_send_busy() can be safely executed if the
>    descriptor parsing fails.
> - Leon points out that target_init_cmd() must receive the
>   actual data direction calculated by srpt_get_desc_tbl(),
>   rather than a placeholder like DMA_NONE that will
>   be overwritten later.
> 
> If we continue to modify the current patch, the only way I
> can think of is to extract the direction parsing logic from
> srpt_get_desc_tbl and place it before target_init_cmd, so
> that target_init_cmd can receive the correct direction.
> How about this?

Say it to your AI tool that it is not contradiction, but wrongly
implemented Bart's suggestion.

Thanks

> 
> Thanks,
> TanZheng