2015-07-21 22:09:06

by Spencer Baugh

Subject: [PATCH] target/iscsi: Fix double free of a TUR followed by a solicited NOPOUT

From: Alexei Potashnik <[email protected]>

Make sure all non-READ SCSI commands get targ_xfer_tag initialized
to 0xffffffff, not just WRITEs.

Double-free of a TUR cmd object occurs under the following scenario:

1. TUR received (targ_xfer_tag is uninitialized and left at 0)
2. TUR status sent
3. First unsolicited NOPIN is sent to initiator (gets targ_xfer_tag of 0)
4. NOPOUT for NOPIN (with TTT=0) arrives
- its ExpStatSN acks TUR status, TUR is queued for removal
- LIO tries to find NOPIN with TTT=0, but finds the same TUR instead,
TUR is queued for removal for the 2nd time

Signed-off-by: Alexei Potashnik <[email protected]>
Signed-off-by: Spencer Baugh <[email protected]>
---
drivers/target/iscsi/iscsi_target.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index a4cf58c..ebb1ece 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -970,7 +970,7 @@ int iscsit_setup_scsi_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
conn->sess->init_task_tag = cmd->init_task_tag = hdr->itt;
if (hdr->flags & ISCSI_FLAG_CMD_READ) {
cmd->targ_xfer_tag = session_get_next_ttt(conn->sess);
- } else if (hdr->flags & ISCSI_FLAG_CMD_WRITE)
+ } else
cmd->targ_xfer_tag = 0xFFFFFFFF;
cmd->cmd_sn = be32_to_cpu(hdr->cmdsn);
cmd->exp_stat_sn = be32_to_cpu(hdr->exp_statsn);
--
2.4.3

2015-07-31 06:10:20

by Nicholas A. Bellinger

Subject: Re: [PATCH] target/iscsi: Fix double free of a TUR followed by a solicited NOPOUT

Hi Spencer & Alexei,

On Tue, 2015-07-21 at 15:07 -0700, Spencer Baugh wrote:
> From: Alexei Potashnik <[email protected]>
>
> Make sure all non-READ SCSI commands get targ_xfer_tag initialized
> to 0xffffffff, not just WRITEs.
>
> Double-free of a TUR cmd object occurs under the following scenario:
>
> 1. TUR received (targ_xfer_tag is uninitialized and left at 0)
> 2. TUR status sent
> 3. First unsolicited NOPIN is sent to initiator (gets targ_xfer_tag of 0)
> 4. NOPOUT for NOPIN (with TTT=0) arrives
> - its ExpStatSN acks TUR status, TUR is queued for removal
> - LIO tries to find NOPIN with TTT=0, but finds the same TUR instead,
> TUR is queued for removal for the 2nd time
>
> Signed-off-by: Alexei Potashnik <[email protected]>
> Signed-off-by: Spencer Baugh <[email protected]>
> ---

Very nice catch on this bug.

> drivers/target/iscsi/iscsi_target.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
> index a4cf58c..ebb1ece 100644
> --- a/drivers/target/iscsi/iscsi_target.c
> +++ b/drivers/target/iscsi/iscsi_target.c
> @@ -970,7 +970,7 @@ int iscsit_setup_scsi_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
> conn->sess->init_task_tag = cmd->init_task_tag = hdr->itt;
> if (hdr->flags & ISCSI_FLAG_CMD_READ) {
> cmd->targ_xfer_tag = session_get_next_ttt(conn->sess);
> - } else if (hdr->flags & ISCSI_FLAG_CMD_WRITE)
> + } else
> cmd->targ_xfer_tag = 0xFFFFFFFF;
> cmd->cmd_sn = be32_to_cpu(hdr->cmdsn);
> cmd->exp_stat_sn = be32_to_cpu(hdr->exp_statsn);

One small nit. linux kernel coding style says conditionals should use
matching brackets. Since it's a single line body, no reason to use
brackets at all.

Applying the updated patch below to target-pending/master with CC' for
3.1 stable.

Thanks!

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index cd77a06..fd09290 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -968,9 +968,9 @@ int iscsit_setup_scsi_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
cmd->cmd_flags |= ICF_NON_IMMEDIATE_UNSOLICITED_DATA;

conn->sess->init_task_tag = cmd->init_task_tag = hdr->itt;
- if (hdr->flags & ISCSI_FLAG_CMD_READ) {
+ if (hdr->flags & ISCSI_FLAG_CMD_READ)
cmd->targ_xfer_tag = session_get_next_ttt(conn->sess);
- } else if (hdr->flags & ISCSI_FLAG_CMD_WRITE)
+ else
cmd->targ_xfer_tag = 0xFFFFFFFF;
cmd->cmd_sn = be32_to_cpu(hdr->cmdsn);
cmd->exp_stat_sn = be32_to_cpu(hdr->exp_statsn);